2.3 mount
Mount: the act of associating an additional file system with an existing directory in the root file system, so that this directory can be used as an access to other files
Uninstall: the process of releasing this association
Associate a device with a mount Point: mount Point
The original files under the mount point will be temporarily hidden after mounting. Therefore, the directory of the mount point is generally empty
The device in use by the process cannot be uninstalled
2.3.1 mount file system
Format:
mount [-fnrsvw] [-t vfstype] [-o options] device mountpoint
Device: indicates the device to mount
- Device file: for example: / dev/sda5
- Volume LABEL: - L 'LABEL', e.g. - L 'MYDATA'
- UUID: - U 'UUID': for example - U '0c50523c-43f1-45e7-85c0-a126711d406e'
- Pseudo file system name: proc, sysfs, devtmpfs, configfs
**mountpoint: * * the mount point directory must exist in advance. It is recommended to use an empty directory
mount common command options
-t fstype Specifies the file system type on the device to mount,as:ext4,xfs
-r readonly，Read only mount
-w read and write, Read write mount
-n Do not update/etc/mtab，mount invisible
-a Auto mount all devices that support auto mount(Defined in/etc/fstab In the file and in the mount option
auto function)
-L 'LABEL' Specify the mount device with the volume label
-U 'UUID' with UUID Specify the device to mount
-B, --bind Bind directory to another directory
-o options: (Options for mounting file systems)，Multiple options are separated by commas
async Asynchronous mode,When memory changes,Write cache buffer,Writing to disk after a period of time is efficient but not safe
sync Synchronous mode,When the memory changes, write to the disk at the same time, which is safe but inefficient
atime/noatime Contains directories and files
diratime/nodiratime Access timestamp of the directory
auto/noauto Whether it supports automatic mount after startup, and whether it supports-a option
exec/noexec Does it support running applications on the file system
dev/nodev Are device files supported on this file system
suid/nosuid Is it supported suid and sgid jurisdiction
remount Remount
ro/rw Read only, read-write
user/nouser Allow ordinary users to mount this device,/etc/fstab use
acl/noacl Enable on this file system acl function
loop use loop equipment
_netdev Mount network resources only when the network is available, such as: NFS file system
defaults amount to rw, suid, dev, exec, auto, nouser, async
Mounting rules:
- A mount point can mount only one device at a time
- If multiple devices are mounted on a mount point at the same time, only the data of the last device can be seen, and the data on other devices will be hidden
- A device can be mounted to multiple mount points at the same time
- Generally, the mount point is an empty directory that already exists
2.3.2 unmount the file system umount
When uninstalling: you can use the device or the mount point
umount Device name|Mount point
2.3.3 viewing mounting
View mount
#Display all currently mounted devices by viewing the / etc/mtab file mount #View all mounted devices tracked by the kernel cat /proc/mounts
View the mount point
findmnt MOUNT_POINT|device
View the processes that are accessing the specified file system
lsof MOUNT_POINT fuser -v MOUNT_POINT
Terminates all processes that are accessing the specified file system
fuser -km MOUNT_POINT
2.3.4 persistent mount
Save the mount in / etc/fstab to enable the mount automatically the next time you power on
/Help in etc/fstab format:
man 5 fstab
Each line defines a file system to mount, including 6 items in total
- Device or pseudo file system to mount
Equipment file
LABEL: LABEL=""
UUID: UUID=""
Pseudo file system name: proc, sysfs - Mount point: must be a pre-existing directory
- File system type: ext4, xfs, iso9660, nfs, none
- Mount options: defaults, acl, bind
- Dump frequency: 0: no backup 1: dump every day 2: dump every other day
- fsck checks the order of file systems: the allowed numbers are 0 1 2
0: no self inspection, 1: self inspection first; Generally, only rootfs is used. 2: non rootfs is used
To add a new mount item, you need to execute the following command to take effect
mount -a
example:
[root@rocky8 ~]# mkdir /mnt/sdb{1,2}
[root@rocky8 ~]# ls /mnt
sdb1 sdb2
[root@rocky8 ~]# ls /mnt/sdb1
[root@rocky8 ~]# touch /mnt/sdb1/sdb1.txt
[root@rocky8 ~]# touch /mnt/sdb2/sdb2.txt
/mnt
├── sdb1
│ └── sdb1.txt
└── sdb2
└── sdb2.txt
2 directories, 2 files
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47636 2039276 3% /mnt
[root@rocky8 ~]# touch /mnt/sdb1/sdb1-2.txt
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47636 2039276 3% /mnt #The first file created, used, is still 47636
[root@rocky8 ~]# touch /mnt/sdb1/sdb1-3.txt
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47636 2039276 3% /mnt #The second file created, used, is still 47636
[root@rocky8 ~]# ll /mnt/sdb1/*
-rw-r--r-- 1 root root 0 Oct 15 22:46 /mnt/sdb1/sdb1-2.txt
-rw-r--r-- 1 root root 0 Oct 15 22:48 /mnt/sdb1/sdb1-3.txt
-rw-r--r-- 1 root root 0 Oct 15 22:45 /mnt/sdb1/sdb1.txt
[root@rocky8 ~]# echo > /mnt/sdb1/sdb1-4.txt
[root@rocky8 ~]# ll /mnt/sdb1/sdb1-4.txt
-rw-r--r-- 1 root root 1 Oct 15 22:51 /mnt/sdb1/sdb1-4.txt
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47660 2039252 3% /mnt #Writing data to a file takes up 4k, because a file takes up a minimum of 4k
[root@rocky8 ~]# du /mnt/sdb1
4 /mnt/sdb1
[root@rocky8 ~]# echo > /mnt/sdb1/sdb1-5.txt
[root@rocky8 ~]# du /mnt/sdb1
8 /mnt/sdb1
#It takes 4k to create a new file
[root@rocky8 ~]# xfs_info /dev/sda2
meta-data=/dev/sda2 isize=512 agcount=4, agsize=6553600 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1
data = bsize=4096 blocks=26214400, imaxpct=25 #Block size 4096
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=12800, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@rocky8 ~]# mount /dev/sdb1 /mnt/sdb1 #Mount mount
[root@rocky8 ~]# ls /mnt/sdb1
lost+found
#After mounting, the original data is invisible and hidden
[root@rocky8 ~]# echo > /mnt/sdb1/a.txt
[root@rocky8 ~]# echo > /mnt/sdb1/b.txt
[root@rocky8 ~]# ls /mnt/sdb1
a.txt b.txt lost+found
[root@rocky8 ~]# du -sh /mnt/sdb1
4.0K /mnt/sdb1
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47644 2039268 3% /mnt
/dev/sdb1 1031836 2821 972491 1% /mnt/sdb1 #2821 disk space has been used
[root@rocky8 ~]# echo > /mnt/sdb1/c.txt
[root@rocky8 ~]# du -sh /mnt/sdb1
5.0K /mnt/sdb1
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47644 2039268 3% /mnt
/dev/sdb1 1031836 2822 972490 1% /mnt/sdb1 #New files add 1k space
[root@rocky8 ~]# ls /mnt/sdb1/ -a
. .. a.txt b.txt c.txt lost+found
[root@rocky8 ~]# umount /mnt/sdb1/
[root@rocky8 ~]# ls /mnt/sdb1/ -a
. .. sdb1-2.txt sdb1-3.txt sdb1-4.txt sdb1-5.txt sdb1.txt
#After uninstalling the partition mount, you can see the data on the original root partition
#As a mount point folder, the first folder must exist and the second folder should be an empty folder
[root@rocky8 ~]# ls /mnt/sdb2
sdb2.txt
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47644 2039268 3% /mnt
[root@rocky8 ~]# mount /dev/sdb2 /mnt/sdb2
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47644 2039268 3% /mnt
#As long as the partition is mounted, it can be seen with df
[root@rocky8 ~]# ls /mnt/sdb2
sdb1 sdb2
#xfs file system takes up more space than ext4 metadata
[root@rocky8 ~]# xfs_info /dev/sdb2
meta-data=/dev/sdb2 isize=512 agcount=4, agsize=131072 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1
data = bsize=4096 blocks=524288, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
#df views data in 1k by default
[root@rocky8 ~]# ls /mnt/sdb2
sdb1 sdb2
[root@rocky8 ~]# echo > /mnt/sdb2/x.txt
[root@rocky8 ~]# ls /mnt/sdb2
sdb1 sdb2 x.txt
[root@rocky8 ~]# du -sh /mnt/sdb2
12K /mnt/sdb2
[root@rocky8 ~]# echo > /mnt/sdb2/y.txt
[root@rocky8 ~]# du -sh /mnt/sdb2
16K /mnt/sdb2
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47652 2039260 3% /mnt
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2 type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
#Mount can also view mount information
[root@rocky8 ~]# mount /dev/sdb1 /mnt/sdb2
[root@rocky8 ~]# ls /mnt/sdb2
a.txt b.txt c.txt lost+found
#A directory can only mount one partition. If multiple partitions are mounted, the files in the original mounted partition will be hidden. You can't see them unless you uninstall the currently mounted partition
[root@rocky8 ~]# umount /mnt/sdb2
[root@rocky8 ~]# ls /mnt/sdb2
sdb1 sdb2 x.txt y.txt
#Unloaded, the original is back
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633816 102172584 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb2 2086912 47652 2039260 3% /mnt
[root@rocky8 ~]# mkdir /mnt/sdb2-2
[root@rocky8 ~]# mount /dev/sdb2 /mnt/sdb2-2
[root@rocky8 ~]# ls /mnt/sdb2-2
sdb1 sdb2 sdb2-2 x.txt y.txt
#A partition can mount multiple mount points, but the data in it is the same
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2 type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
#reltime delays updating the read time. Only when the read time reaches more than one day, or when the read time is older than the write time, can it be updated. Only when the file is added, can it appear that the read time is earlier than the modification time. Only at this time can the read time be updated
#You can add noatime and nodiratime when you mount it, and it will not update the read time, but if you touch the file, it will still update the read time
[root@rocky8 ~]# touch /mnt/sdb2/xx.txt
[root@rocky8 ~]# cd /mnt/sdb2
#If someone is accessing the directory
[root@rocky8 sdb2]# umount /mnt/sdb2
umount: /mnt/sdb2: target is busy.
#You cannot unmount the mounted partition now
[root@rocky8 sdb2]# fuser -v /mnt/sdb2 #fuser -v see who is accessing this directory
USER PID ACCESS COMMAND
/mnt/sdb2: root kernel mount /mnt
root 917 ..c.. bash
[root@rocky8 sdb2]# fuser -mk /mnt/sdb2 #fuser -mk can force users using this directory out
/mnt/sdb2: 917c
Connection closed.
Disconnected from remote host(rocky8.4-172.31.1.8) at 23:07:17.
Type `help' to learn how to use Xshell prompt.
[C:\~]$
Reconnecting in 1 seconds. Press any key to exit local shell.
.
Connecting to 172.31.1.8:22...
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.
WARNING! The remote SSH server rejected X11 forwarding request.
Last login: Fri Oct 15 19:09:34 2021 from 172.31.0.1
[root@rocky8 ~]#
#The user who kicks the access will log out
[root@rocky8 ~]# fuser -v /mnt/sdb2
USER PID ACCESS COMMAND
/mnt/sdb2: root kernel mount /mnt
#No one is visiting now
[root@rocky8 ~]# umount /mnt/sdb2
#Just cancel the mount now
[root@rocky8 ~]# mount /dev/sdb2 /mnt/sdb2
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
[root@rocky8 ~]# mount -o remount,ro /mnt/sdb2
#Remount with mount -o remount without kicking the user who is accessing
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota) #This is already read-only
[root@rocky8 ~]# touch /mnt/sdb2/yy.txt
touch: cannot touch '/mnt/sdb2/yy.txt': Read-only file system
#You can't write files in now
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633912 102172488 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 191796 846540 19% /boot
/dev/sdb2 2086912 336 2086576 1% /mnt
tmpfs 80116 0 80116 0% /run/user/0
[root@rocky8 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 100G 0 part /
├─sda3 8:3 0 50G 0 part /data
├─sda4 8:4 0 1K 0 part
└─sda5 8:5 0 2G 0 part [SWAP]
sdb 8:16 0 20G 0 disk
├─sdb1 8:17 0 1G 0 part
├─sdb2 8:18 0 2G 0 part /mnt/sdb2
├─sdb3 8:19 0 512B 0 part
├─sdb5 8:21 0 2G 0 part
└─sdb6 8:22 0 3G 0 part
sdc 8:32 0 10G 0 disk
├─sdc1 8:33 0 1G 0 part
└─sdc2 8:34 0 2G 0 part
sr0 11:0 1 9.2G 0 rom
nvme0n1 259:0 0 10G 0 disk
[root@rocky8 ~]# umount /boot
[root@rocky8 ~]# umount /data
[root@rocky8 ~]# umount /
umount: /: target is busy.
#/The root partition cannot be unmounted
[root@rocky8 ~]# mount -a
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633932 102172468 3% /
/dev/sdb2 2086912 336 2086576 1% /mnt
tmpfs 80116 0 80116 0% /run/user/0
/dev/sda1 1038336 191796 846540 19% /boot
/dev/sda3 52403200 398404 52004796 1% /data
[root@rocky8 ~]# findmnt /data
TARGET SOURCE FSTYPE OPTIONS
/data /dev/sda3 xfs rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota
#findmnt view mount status
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2633912 102172488 3% /
/dev/sdb2 2086912 336 2086576 1% /mnt
tmpfs 80116 0 80116 0% /run/user/0
/dev/sda1 1038336 191796 846540 19% /boot
/dev/sda3 52403200 398404 52004796 1% /data
[root@rocky8 ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Wed Oct 6 11:16:34 2021
#
# Accessible filesystems, by reference, are maintained under '/dev/disk/'.
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.
#
# After editing this file, run 'systemctl daemon-reload' to update systemd
# units generated from this file.
#
UUID=57f3a077-bb67-42c3-9e6c-bc8a0fed3776 / xfs defaults 0 0
UUID=c72110fc-5dae-470c-9940-97ba978c7dc7 /boot xfs defaults 0 0
UUID=02ae6744-8c28-4c86-b85b-e113c06a834f /data xfs defaults 0 0
UUID=4f387202-0a81-4202-9e12-90d04af4d308 none swap defaults 0 0
[root@rocky8 ~]# lsblk -f
NAME FSTYPE LABEL UUID MOUNTPOINT
sda
├─sda1 xfs c72110fc-5dae-470c-9940-97ba978c7dc7 /boot
├─sda2 xfs 57f3a077-bb67-42c3-9e6c-bc8a0fed3776 /
├─sda3 xfs 02ae6744-8c28-4c86-b85b-e113c06a834f /data
├─sda4
└─sda5 swap 4f387202-0a81-4202-9e12-90d04af4d308 [SWAP]
sdb
├─sdb1 ext4 f7d5345f-5f29-417d-a044-37508852e80f
├─sdb2 xfs 8a2c8fdf-9294-4030-b10c-edc8a7b3e78f /mnt/sdb2
├─sdb3
├─sdb5
└─sdb6
sdc
├─sdc1
└─sdc2
sr0 iso9660 Rocky-8-4-x86_64-dvd 2021-06-20-16-16-21-00
nvme0n1
[root@rocky8 ~]# blkid /dev/sdb1
/dev/sdb1: UUID="f7d5345f-5f29-417d-a044-37508852e80f" BLOCK_SIZE="1024" TYPE="ext4" PARTUUID="a62c9118-01"
[root@rocky8 ~]# vim /etc/fstab
#Add the following
UUID=f7d5345f-5f29-417d-a044-37508852e80f /mnt/sdb1 ext4 ro,noatime,nodiratime 0 0
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sdb2 on /mnt type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
#Now / dev/sdb1 is not mounted
[root@rocky8 ~]# mount -a #mount -a mount now
[root@rocky8 ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sdb2 on /mnt type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb1 on /mnt/sdb1 type ext4 (ro,noatime,nodiratime)
#Now / dev/sdb1 is mounted
[root@rocky8 ~]# cd /mnt/sdb1
[root@rocky8 sdb1]# ls
a.txt b.txt c.txt lost+found
[root@rocky8 sdb1]# rm -f a.txt
rm: cannot remove 'a.txt': Read-only file system
#Because it is mounted read-only, the files in it cannot be deleted now
[root@rocky8 sdb1]# vim /etc/fstab
UUID=f7d5345f-5f29-417d-a044-37508852e80f /mnt/sdb1 ext4 noatime,nodiratime 0 0
#Delete ro, and the default is rw
[root@rocky8 sdb1]# mount -a
[root@rocky8 sdb1]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sdb2 on /mnt type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb1 on /mnt/sdb1 type ext4 (ro,noatime,nodiratime)
#mount -a does not take effect immediately
[root@rocky8 sdb1]# mount -o remount /dev/sdb1 #remount must be remounted
[root@rocky8 sdb1]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,size=382688k,nr_inodes=95672,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
none on /sys/kernel/tracing type tracefs (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/dev/sda2 on / type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=37,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=22459)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
/dev/sdb2 on /mnt type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb2 on /mnt/sdb2-2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
tmpfs on /run/user/0 type tmpfs (rw,nosuid,nodev,relatime,size=80116k,mode=700)
/dev/sdb2 on /mnt/sdb2 type xfs (ro,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda3 on /data type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sdb1 on /mnt/sdb1 type ext4 (rw,noatime,nodiratime)
#It takes effect now
#If mount -a has never existed in / etc/fstab, the new one will take effect immediately. If it already exists, the changed one will not take effect immediately
[root@rocky8 sdb1]# cd /mnt/sdb1
[root@rocky8 sdb1]# ls
a.txt b.txt c.txt lost+found
[root@rocky8 sdb1]# rm -rf lost+found/
[root@rocky8 sdb1]# ls
a.txt b.txt c.txt
#Now you can delete the files or folders inside. The lost+found folder is a feature of ext2, ext3 and etx4, which is equivalent to a shelter
[root@rocky8 sdb1]# stat b.txt
File: b.txt
Size: 1 Blocks: 2 IO Block: 1024 regular file
Device: 811h/2065d Inode: 13 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2021-10-15 22:55:26.196775264 +0800
Modify: 2021-10-15 22:55:26.196775264 +0800
Change: 2021-10-15 22:55:26.196775264 +0800
Birth: -
[root@rocky8 sdb1]# cat b.txt
[root@rocky8 sdb1]# stat b.txt
File: b.txt
Size: 1 Blocks: 2 IO Block: 1024 regular file
Device: 811h/2065d Inode: 13 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2021-10-15 22:55:26.196775264 +0800
Modify: 2021-10-15 22:55:26.196775264 +0800
Change: 2021-10-15 22:55:26.196775264 +0800
Birth: -
#Cat atime is not modified
[root@rocky8 sdb1]# touch b.txt
[root@rocky8 sdb1]# stat b.txt
File: b.txt
Size: 1 Blocks: 2 IO Block: 1024 regular file
Device: 811h/2065d Inode: 13 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2021-10-15 23:21:03.783761878 +0800
Modify: 2021-10-15 23:21:03.783761878 +0800
Change: 2021-10-15 23:21:03.783761878 +0800
Birth: -
#Forced touch, atime is modified
[root@rocky8 sdb1]# reboot
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5748 394832 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2632648 102173752 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 192152 846184 19% /boot
/dev/sdb1 1031836 2821 972491 1% /mnt/sdb1
tmpfs 80116 0 80116 0% /run/user/0
#After reboot, / dev/sdb1 is automatically mounted
[root@rocky8 ~]# vim /etc/fstab
UUID=f7d5345f-5f29-417d-a044-37508852e800 /mnt/sdb1 ext4 noatime,nodiratime 0 0
#If the UUID is written incorrectly during setting, the system cannot start normally after restarting
[root@rocky8 ~]# reboot
#It will enter the fault state and enter the root password
#Check that / dev/sdb1 is not mounted
#Enter configuration file
#Note out the line of attaching the wrong disk first
#Restart
#Now the system can start normally
[root@rocky8 ~]# vim /etc/fstab /dev/sdb1 /mnt/sdb1 ext4 noatime,nodiratime 0 0 [root@rocky8 ~]# mount -a [root@rocky8 ~]# df Filesystem 1K-blocks Used Available Use% Mounted on devtmpfs 382688 0 382688 0% /dev tmpfs 400580 0 400580 0% /dev/shm tmpfs 400580 5744 394836 2% /run tmpfs 400580 0 400580 0% /sys/fs/cgroup /dev/sda2 104806400 2632880 102173520 3% / /dev/sda3 52403200 398404 52004796 1% /data /dev/sda1 1038336 192152 846184 19% /boot tmpfs 80116 0 80116 0% /run/user/0 /dev/sdb1 1031836 2821 972491 1% /mnt/sdb1
Example: the UUID of centos7,8 / etc / fstab partition is wrong and cannot be started
Automatic entry emergency mode,input root password #cat /proc/mounts can be viewed / mounted in rw mode #vim /etc/fstab #reboot
Example: the UUID of centos 6 /etc/fstab partition is wrong and cannot be started
#If the mount device of / etc/fstab fails, such as file system failure, and the file system detection item (i.e. item 6 is non-0), it will fail to start #Automatically enter emergency mode and enter the root password #cat /proc/mounts can be viewed / mounted in ro mode, and the configuration file cannot be modified directly #mount -o remount,rw / #vim /etc/fstab #Modify the last item of the fault line, i.e. item 6, to 0. The health of the mounted equipment will not be detected during startup, so as to ignore the error and realize startup
Example: / etc/fstab format
[root@centos8 ~]#cat /etc/fstab UUID=cb7cae1e-d227-4f64-872b-cd6cce20c911 /data/mysql ext4 noatime 0 0 /disk.img data/disk xfs defaults 0 0 /etc /mnt/etc none bind 0 0 [root@centos6 ~]#cat /etc/fstab /disk.img /mnt/disk ext4 loop 0 0
2.4 processing exchange files and partitions
2.4.1 introduction to swap
Swap swap partition is a supplement to system RAM. Swap partition supports virtual memory. When there is not enough ram to save the data processed by the system, the data will be written to the swap partition. When the system lacks swap space, the kernel will terminate the process due to the depletion of RAM memory. Configuring too much swap space will cause the storage device to be allocated but idle, resulting in waste. Too much swap space will also cover up memory leakage
Note: to optimize performance, swap can be stored in distributed storage or high-performance disk storage
Official recommendation system swap space
https://access.redhat.com/documentation/zh-cn/red_hat_enterprise_linux/7/html/installation_guide/sect-disk-partitioning-setup-ppc#sect-recommended-partitioning-scheme-ppc
| Amount of RAM in the system | Recommended swap space | Recommended swap space size to allow hibernation |
|---|---|---|
| Less than 2 GB | 2 times the amount of RAM | Three times the RAM capacity |
| 2 GB - 8 GB | Equal to the amount of RAM | Multiple of RAM |
| 8 GB - 64 GB | 4 GB to 0.5 times RAM capacity | 1.5 times RAM capacity |
| Over 64 GB | Independent load (at least 4GB) | Hibernation is not recommended |
example:
[root@rocky8 ~]# free -h
total used free shared buff/cache available
Mem: 782Mi 178Mi 396Mi 5.0Mi 207Mi 470Mi
Swap: 2.0Gi 0B 2.0Gi
#If the memory is full and there is no virtual memory, an OOM error will appear. OOM is out of memory. The memory is full
[root@rocky8 ~]# dd if=/dev/zero of=/dev/null bs=8G count=1
dd: memory exhausted by input buffer of size 8589934592 bytes (8.0 GiB)
#If you use 8G of memory immediately, you will report that there is insufficient memory
[root@rocky8 ~]# dd if=/dev/zero of=/dev/null bs=4G count=1
dd: memory exhausted by input buffer of size 4294967296 bytes (4.0 GiB)
[root@rocky8 ~]# dd if=/dev/zero of=/dev/null bs=100M count=1
1+0 records in
1+0 records out
104857600 bytes (105 MB, 100 MiB) copied, 0.0722939 s, 1.5 GB/s
[root@rocky8 ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xa62c9118
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 2099199 2097152 1G 83 Linux
/dev/sdb2 2099200 6293503 4194304 2G 83 Linux
/dev/sdb3 6293504 41943039 35649536 17G 5 Extended
/dev/sdb5 6295552 10489855 4194304 2G 83 Linux
/dev/sdb6 10491904 16783359 6291456 3G 8e Linux LVM
[root@rocky8 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 100G 0 part /
├─sda3 8:3 0 50G 0 part /data
├─sda4 8:4 0 1K 0 part
└─sda5 8:5 0 2G 0 part [SWAP]
sdb 8:16 0 20G 0 disk
├─sdb1 8:17 0 1G 0 part /mnt/sdb1
├─sdb2 8:18 0 2G 0 part
├─sdb3 8:19 0 1K 0 part
├─sdb5 8:21 0 2G 0 part
└─sdb6 8:22 0 3G 0 part
sdc 8:32 0 10G 0 disk
├─sdc1 8:33 0 1G 0 part
└─sdc2 8:34 0 2G 0 part
sr0 11:0 1 9.2G 0 rom
nvme0n1 259:0 0 10G 0 disk
[root@rocky8 ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 382688 0 382688 0% /dev
tmpfs 400580 0 400580 0% /dev/shm
tmpfs 400580 5744 394836 2% /run
tmpfs 400580 0 400580 0% /sys/fs/cgroup
/dev/sda2 104806400 2632880 102173520 3% /
/dev/sda3 52403200 398404 52004796 1% /data
/dev/sda1 1038336 192152 846184 19% /boot
tmpfs 80116 0 80116 0% /run/user/0
/dev/sdb1 1031836 2821 972491 1% /mnt/sdb1
[root@rocky8 ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): t
Partition number (1-3,5,6, default 6): 5
Hex code (type L to list all codes): L
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 27 Hidden NTFS Win 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 39 Plan 9 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 3c PartitionMagic 84 OS/2 hidden or c6 DRDOS/sec (FAT-
4 FAT16 <32M 40 Venix 80286 85 Linux extended c7 Syrinx
5 Extended 41 PPC PReP Boot 86 NTFS volume set da Non-FS data
6 FAT16 42 SFS 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS/exFAT 4d QNX4.x 88 Linux plaintext de Dell Utility
8 AIX 4e QNX4.x 2nd part 8e Linux LVM df BootIt
9 AIX bootable 4f QNX4.x 3rd part 93 Amoeba e1 DOS access
a OS/2 Boot Manag 50 OnTrack DM 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 51 OnTrack DM6 Aux 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 52 CP/M a0 IBM Thinkpad hi ea Rufus alignment
e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD eb BeOS fs
f W95 Ext'd (LBA) 54 OnTrackDM6 a6 OpenBSD ee GPT
10 OPUS 55 EZ-Drive a7 NeXTSTEP ef EFI (FAT-12/16/
11 Hidden FAT12 56 Golden Bow a8 Darwin UFS f0 Linux/PA-RISC b
12 Compaq diagnost 5c Priam Edisk a9 NetBSD f1 SpeedStor
14 Hidden FAT16 <3 61 SpeedStor ab Darwin boot f4 SpeedStor
16 Hidden FAT16 63 GNU HURD or Sys af HFS / HFS+ f2 DOS secondary
17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fb VMware VMFS
18 AST SmartSleep 65 Novell Netware b8 BSDI swap fc VMware VMKCORE
1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid fd Linux raid auto
1c Hidden W95 FAT3 75 PC/IX bc Acronis FAT32 L fe LANstep
1e Hidden W95 FAT1 80 Old Minix be Solaris boot ff BBT
Hex code (type L to list all codes): 82
Changed type of partition 'Linux' to 'Linux swap / Solaris'.
Command (m for help): p
Disk /dev/sdb: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xa62c9118
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 2099199 2097152 1G 83 Linux
/dev/sdb2 2099200 6293503 4194304 2G 83 Linux
/dev/sdb3 6293504 41943039 35649536 17G 5 Extended
/dev/sdb5 6295552 10489855 4194304 2G 82 Linux swap / Solaris #Change / dev/sdb5 to swap
/dev/sdb6 10491904 16783359 6291456 3G 8e Linux LVM
Command (m for help): w
The partition table has been altered.
Syncing disks.
[root@rocky8 ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xa62c9118
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 2099199 2097152 1G 83 Linux
/dev/sdb2 2099200 6293503 4194304 2G 83 Linux
/dev/sdb3 6293504 41943039 35649536 17G 5 Extended
/dev/sdb5 6295552 10489855 4194304 2G 82 Linux swap / Solaris
/dev/sdb6 10491904 16783359 6291456 3G 8e Linux LVM
[root@rocky8 ~]# mkswap /dev/sdb5 #mkswap create swap partition
Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)
no label, UUID=9a3b3cde-e94d-4f62-9c7e-069d2e3e400b
[root@rocky8 ~]# blkid
/dev/sda2: UUID="57f3a077-bb67-42c3-9e6c-bc8a0fed3776" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="43d7507d-02"
/dev/sda1: UUID="c72110fc-5dae-470c-9940-97ba978c7dc7" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="43d7507d-01"
/dev/sda3: UUID="02ae6744-8c28-4c86-b85b-e113c06a834f" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="43d7507d-03"
/dev/sda5: UUID="4f387202-0a81-4202-9e12-90d04af4d308" TYPE="swap" PARTUUID="43d7507d-05"
/dev/sdb1: UUID="f7d5345f-5f29-417d-a044-37508852e80f" BLOCK_SIZE="1024" TYPE="ext4" PARTUUID="a62c9118-01"
/dev/sdb2: UUID="8a2c8fdf-9294-4030-b10c-edc8a7b3e78f" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="a62c9118-02"
/dev/sdb5: UUID="9a3b3cde-e94d-4f62-9c7e-069d2e3e400b" TYPE="swap" PARTUUID="a62c9118-05"
/dev/sdb6: PARTUUID="a62c9118-06"
/dev/sdc1: PARTLABEL="Linux filesystem" PARTUUID="7a7090a5-623a-45a0-b7e7-2c613355b7ea"
/dev/sdc2: PARTLABEL="Linux LVM" PARTUUID="cb838081-f185-4983-ad7e-6eea78c54565"
/dev/sr0: BLOCK_SIZE="2048" UUID="2021-06-20-16-16-21-00" LABEL="Rocky-8-4-x86_64-dvd" TYPE="iso9660" PTUUID="4a14a4ee" PTTYPE="dos"
[root@rocky8 ~]# vim /etc/fstab
UUID=9a3b3cde-e94d-4f62-9c7e-069d2e3e400b swap swap defaults 0 0
[root@rocky8 ~]# swapon -a #Effective immediately
[root@rocky8 ~]# swapon -s #View swap
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -2
/dev/sdb5 partition 2097148 0 -3
#-2, - 3 is the priority. The smaller the number, the higher the priority. It is used first
[root@rocky8 ~]# free -h
total used free shared buff/cache available
Mem: 782Mi 179Mi 391Mi 5.0Mi 210Mi 469Mi
Swap: 4.0Gi 0B 4.0Gi
#swap increased by 2G
#To delete swap, ensure that the deleted partition is not used
[root@rocky8 ~]# vim /etc/fstab
UUID=9a3b3cde-e94d-4f62-9c7e-069d2e3e400b swap swap pri=100 0 0
#pre=100 is to set the priority. The set positive priority is higher than the system default negative priority
[root@rocky8 ~]# swapoff /dev/sdb5
[root@rocky8 ~]# swapon -a
[root@rocky8 ~]# swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -2
/dev/sdb5 partition 2097148 0 100
#Delete swap
[root@rocky8 ~]# swapoff /dev/sdb5 #Close / dev/sdb5 and swap first
[root@rocky8 ~]# vim /etc/fstab
#Delete the following
UUID=9a3b3cde-e94d-4f62-9c7e-069d2e3e400b swap swap pri=100 0 0
[root@rocky8 ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): d
Partition number (1-3,5,6, default 6): 5
Partition 5 has been deleted.
Command (m for help): w
The partition table has been altered.
Syncing disks.
#delete a partition
[root@rocky8 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 100G 0 part /
├─sda3 8:3 0 50G 0 part /data
├─sda4 8:4 0 1K 0 part
└─sda5 8:5 0 2G 0 part [SWAP]
sdb 8:16 0 20G 0 disk
├─sdb1 8:17 0 1G 0 part /mnt/sdb1
├─sdb2 8:18 0 2G 0 part
├─sdb3 8:19 0 1K 0 part
└─sdb5 8:21 0 3G 0 part
sdc 8:32 0 10G 0 disk
├─sdc1 8:33 0 1G 0 part
└─sdc2 8:34 0 2G 0 part
sr0 11:0 1 9.2G 0 rom
nvme0n1 259:0 0 10G 0 disk
[root@rocky8 ~]# swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -2
[root@rocky8 ~]# free -h
total used free shared buff/cache available
Mem: 782Mi 181Mi 333Mi 5.0Mi 267Mi 467Mi
Swap: 2.0Gi 0B 2.0Gi
[root@rocky8 ~]# swapoff /dev/sda5 #Remove what / dev/sda5 is using
[root@rocky8 ~]# free -h
total used free shared buff/cache available
Mem: 782Mi 179Mi 336Mi 5.0Mi 266Mi 468Mi
Swap: 0B 0B 0B
#Now the memory usage becomes larger and the swap partition is gone
2.4.2 implementation process of switching partition
- Create swap partition or file
- Write special signatures using mkswap
- Add the appropriate entry in the / etc/fstab file
- Activate swap space with swapon -a
Enable swap partition
swapon [OPTION]... [DEVICE]
Options:
-a: Activate all switched partitions -p PRIORITY: Specify priority, or/etc/fstab Specify in column 4: pri=value
Example: create swap partition
[root@rocky8 ~]# echo -e 'n\np\n\n\n+2G\nt\n82\nw\n' | fdisk /dev/sdc [root@rocky8 ~]# mkswap /dev/sdc1 Setting up swapspace version 1, size = 2 GiB (2147479552 bytes) no label, UUID=d3140a7a-65b7-4cb7-8a2b-12d38aa98c6f [root@rocky8 ~]# blkid /dev/sdc1 /dev/sdc1: UUID="d3140a7a-65b7-4cb7-8a2b-12d38aa98c6f" TYPE="swap" PARTUUID="b094d43d-01 [root@rocky8 ~]# vim /etc/fstab UUID=d3140a7a-65b7-4cb7-8a2b-12d38aa98c6f swap swap defaults,pri=100 0 0 [root@rocky8 ~]# swapon -a [root@rocky8 ~]# free -h total used free shared buff/cache available Mem: 3.7Gi 264Mi 3.2Gi 9.0Mi 261Mi 3.2Gi Swap: 4.0Gi 0B 4.0Gi [root@rocky8 ~]# cat /proc/swaps Filename Type Size Used Priority /dev/sda5 partition 2097148 0 -2 /dev/sdc1 partition 2097148 0 100
Disable swap partition:
swapoff [OPTION]... [DEVICE]
Example: disable swap partition
[root@rocky8 ~]# sed -i.bak '/swap/d' /etc/fstab [root@rocky8 ~]# swapoff -a
Priority of SWAP
You can specify the priority of swap partitions 0 to 32767. The higher the value, the higher the priority
If the user does not specify a priority, the core will automatically assign a priority to the swap, starting from - 1. Each time a new swap without a priority specified by the user is added, the priority will be reduced by one
The default priority of the first added swap is relatively high, unless the user specifies a priority, and the priority specified by the user (a positive number) is always higher than the priority specified by the core default (a negative number)
2.4.3 usage strategy of swap
/The value of proc/sys/vm/swappiness determines the space of swap partition when the memory consumption reaches a certain percentage
example:
[root@centos8 ~]# cat /proc/sys/vm/swappiness 30 [root@rhel5 ~]# cat /proc/sys/vm/swappiness 60
Note: when the memory is used to 100-30 = 70%, swap partitions begin to be used. Simply put, this parameter defines the system's tendency to use swap. The default value is 30. The larger the value, the more inclined it is to use swap. It can be set to 0, which will not prohibit the use of swap, but minimize the possibility of using swap
example:
[root@rocky8 ~]# cat /proc/sys/vm/swappiness 30 [root@rocky8 ~]# echo "vm.swappiness=0" >> /etc/sysctl.conf [root@rocky8 ~]# sysctl -p vm.swappiness = 0 [root@rocky8 ~]# cat /proc/sys/vm/swappiness 0
2.5 common disk tools
2.5.1 file system space occupation and other information viewing tools df
df [OPTION]... [FILE]...
Common options
-H Unit: 10 -T file system type -h human-readable -i inodes instead of blocks -P with Posix Compatible format output
example:
[[root@rocky8 ~]# df Filesystem 1K-blocks Used Available Use% Mounted on devtmpfs 382688 0 382688 0% /dev tmpfs 400580 0 400580 0% /dev/shm tmpfs 400580 5740 394840 2% /run tmpfs 400580 0 400580 0% /sys/fs/cgroup /dev/sda2 104806400 2633380 102173020 3% / /dev/sda3 52403200 398404 52004796 1% /data /dev/sda1 1038336 192152 846184 19% /boot /dev/sdb1 1031836 2821 972491 1% /mnt/sdb1 tmpfs 80116 0 80116 0% /run/user/0 [root@rocky8 ~]# df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 374M 0 374M 0% /dev tmpfs 392M 0 392M 0% /dev/shm tmpfs 392M 5.7M 386M 2% /run tmpfs 392M 0 392M 0% /sys/fs/cgroup /dev/sda2 100G 2.6G 98G 3% / /dev/sda3 50G 390M 50G 1% /data /dev/sda1 1014M 188M 827M 19% /boot /dev/sdb1 1008M 2.8M 950M 1% /mnt/sdb1 tmpfs 79M 0 79M 0% /run/user/0 [root@rocky8 ~]# df -Th #-T display file system Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 374M 0 374M 0% /dev tmpfs tmpfs 392M 0 392M 0% /dev/shm tmpfs tmpfs 392M 5.7M 386M 2% /run tmpfs tmpfs 392M 0 392M 0% /sys/fs/cgroup /dev/sda2 xfs 100G 2.6G 98G 3% / /dev/sda3 xfs 50G 390M 50G 1% /data /dev/sda1 xfs 1014M 188M 827M 19% /boot /dev/sdb1 ext4 1008M 2.8M 950M 1% /mnt/sdb1 tmpfs tmpfs 79M 0 79M 0% /run/user/0
example:
[root@rhel5 ~]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/mapper/VolGroup00-LogVol00 99415464 2084776 92199220 3% / /dev/sda1 101086 12056 83811 13% /boot tmpfs 517536 0 517536 0% /dev/shm [root@rhel5 ~]# df -P Filesystem 1024-blocks Used Available Capacity Mounted on /dev/mapper/VolGroup00-LogVol00 99415464 2084776 92199220 3% / /dev/sda1 101086 12056 83811 13% /boot tmpfs
2.5.2 view the overall space occupancy of a directory du
du [OPTION]... DIR
Common options
-h human-readable
-s summary
--max-depth=# Specify the maximum directory level
-x, --one-file-system #Ignore directories that are not on the same file system
example:
[root@rocky8 ~]# du /data
4 /data
[root@rocky8 ~]# echo a>/data/a.txt
[root@rocky8 ~]# du /data
8 /data
[root@rocky8 ~]# du -h /data
8.0K /data
[root@rocky8 ~]# mkdir /data/dir{1,2}
[root@rocky8 ~]# echo b >/data/dir1/b.txt
[root@rocky8 ~]# echo c >/data/dir2/c.txt
[root@rocky8 ~]# du /data
4 /data/dir1
4 /data/dir2
16 /data
[root@rocky8 ~]# du -sh /data
16K /data
#-s displays only the / data directory information
2.5.3 tools dd
dd command: convert and copy a file
Format:
dd if=/PATH/FROM/SRC of=/PATH/TO/DEST bs=# count=#
Common options
if=file Read from the named file instead of from standard input of=file Write to the named file instead of to standard output bs=size block size, Specify block size (yes ibs Also obs) cbs=size Primary conversion size individual byte skip=blocks Ignore from beginning blocks individual ibs Block size seek=blocks Ignore from beginning blocks individual obs Block size count=n copy n individual bs conv=conversion[,conversion...] Converts the file with the specified parameters conversion Conversion parameters: ascii transformation EBCDIC by ASCII ebcdic transformation ASCII by EBCDIC lcase Convert uppercase characters to lowercase characters ucase Convert lowercase characters to uppercase characters nocreat Do not create output file noerror Don't stop on error notrunc Do not truncate output files sync Fill each input block into ibs Bytes, and the insufficient part is empty(NUL)Character complement fdatasync The output file is physically written before writing is complete
example:
#skip is the number of skips when inputting from the if target #seek is the number of skips when outputting from the of target [root@rocky8 ~]# dd of=/data/a.txt conv=ucase #Convert case abc xyz 0+2 records in 0+1 records out 8 bytes copied, 24.516 s, 0.0 kB/s #ctrl+d end [root@rocky8 ~]# cat /data/a.txt ABC XYZ [root@rocky8 ~]# cat >f1.txt <<EOF abcdef EOF [root@rocky8 ~]# cat >f2.txt <<EOF 123456789 EOF [root@rocky8 ~]# dd if=f1.txt of=f2.txt bs=1 count=2 skip=3 seek=4 2+0 records in 2+0 records out 2 bytes copied, 8.4238e-05 s, 23.7 kB/s [root@rocky8 ~]# cat f2.txt 1234de # bs=1 reads 1 byte each time, count=2 reads 2 times, skip=3 skips 3 from f1.txt, seek=4 skips 4 from f2.txt, and outputs to f2.txt. The last F of f1.txt is truncated, and the 789 of f2.txt is truncated, so it doesn't exist. The final result is 1234de. [root@rocky8 ~]# cat >f2.txt <<EOF 123456789 EOF [root@rocky8 ~]# cat f1.txt abcdef [root@rocky8 ~]# cat f2.txt 123456789 [root@rocky8 ~]# dd if=f1.txt of=f2.txt bs=1 count=2 skip=3 seek=4 conv=notrunc 2+0 records in 2+0 records out 2 bytes copied, 9.5318e-05 s, 21.0 kB/s [root@rocky8 ~]# cat f2.txt 1234de789 #conv=notrunc this is not truncation [root@rocky8 ~]# dd if=/dev/zero of=/data/disk.img bs=1M count=0 seek=1024 0+0 records in 0+0 records out 0 bytes copied, 3.1539e-05 s, 0.0 kB/s [root@rocky8 ~]# du /data/disk.img 0 /data/disk.img #What is created is a sparse file, or an empty file
example:
#Backup MBR dd if=/dev/sda of=/tmp/mbr.bak bs=512 count=1 #Destroy bootloader in MBR dd if=/dev/zero of=/dev/sda bs=64 count=1 seek=446
2.6 practice
1. Create a 2G file system with a block size of 2048byte and 1% of the available space reserved. The file system is ext4 and the volume label is test. This partition is required to be automatically mounted to the / test directory after startup, and the acl mount option is available by default
2. Write a script to complete the following functions:
(1) Lists all disk devices recognized by the current system
(2) If the number of disks is 1, its space usage information is displayed
Otherwise, space usage information on the last disk is displayed
3. Merge the CentOS-6.10-x86_64-bin-DVD1.iso and CentOS-6.10-x86_64-bin-DVD2.iso files of CentOS6 into a CentOS-6.10-x86_64-Everything.iso file, and configure it as a yum source