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33.第九章 磁盘存储和文件系统管理(三)

作者:互联网

2.3 挂载

挂载:将额外文件系统与根文件系统某现存的目录建立起关联关系,进而使得此目录做为其它文件访问入口的行为

卸载:为解除此关联关系的过程

把设备关联挂载点:mount Point

挂载点下原有文件在挂载完成后会被临时隐藏,因此,挂载点目录一般为空

进程正在使用中的设备无法被卸载

2.3.1 挂载文件系统 mount

格式:

mount [-fnrsvw] [-t vfstype] [-o options] device mountpoint

device:指明要挂载的设备

**mountpoint:**挂载点目录必须事先存在,建议使用空目录

mount常用命令选项

-t fstype 指定要挂载的设备上的文件系统类型,如:ext4,xfs
-r readonly,只读挂载
-w read and write, 读写挂载
-n 不更新/etc/mtab,mount不可见
-a 自动挂载所有支持自动挂载的设备(定义在了/etc/fstab文件中,且挂载选项中有
auto功能)
-L 'LABEL' 以卷标指定挂载设备
-U 'UUID' 以UUID指定要挂载的设备
-B, --bind 绑定目录到另一个目录上

-o options:(挂载文件系统的选项),多个选项使用逗号分隔
    async 异步模式,内存更改时,写入缓存区buffer,过一段时间再写到磁盘中,效率高,但不安全
    sync 同步模式,内存更改时,同时写磁盘,安全,但效率低下
    atime/noatime 包含目录和文件
    diratime/nodiratime 目录的访问时间戳
    auto/noauto 是否支持开机自动挂载,是否支持-a选项
    exec/noexec 是否支持将文件系统上运行应用程序
    dev/nodev 是否支持在此文件系统上使用设备文件
    suid/nosuid 是否支持suid和sgid权限
    remount 重新挂载
    ro/rw 只读、读写
    user/nouser 是否允许普通用户挂载此设备,/etc/fstab使用
    acl/noacl 启用此文件系统上的acl功能
    loop 使用loop设备
    _netdev 当网络可用时才对网络资源进行挂载,如:NFS文件系统
    defaults 相当于rw, suid, dev, exec, auto, nouser, async

挂载规则:

2.3.2 卸载文件系统 umount

卸载时:可使用设备,也可以使用挂载点

umount 设备名|挂载点

2.3.3 查看挂载情况

查看挂载

#通过查看/etc/mtab文件显示当前已挂载的所有设备
mount
#查看内核追踪到的已挂载的所有设备
cat /proc/mounts

查看挂载点情况

findmnt MOUNT_POINT|device

查看正在访问指定文件系统的进程

lsof MOUNT_POINT
fuser -v MOUNT_POINT

终止所有在正访问指定的文件系统的进程

fuser -km MOUNT_POINT

2.3.4 持久挂载

将挂载保存到 /etc/fstab 中可以下次开机时,自动启用挂载

/etc/fstab格式帮助:

man 5 fstab

每行定义一个要挂载的文件系统,,其中包括共 6 项

添加新的挂载项,需要执行下面命令生效

mount -a

范例:

[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 #创建的第一个文件used没有变化,还是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 #创建的第二个文件used没有变化,还是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 #给文件写数据占用4k大小,因为一个文件最小占用4k大小空间

[root@rocky8 ~]# du /mnt/sdb1
4	/mnt/sdb1
[root@rocky8 ~]# echo > /mnt/sdb1/sdb1-5.txt
[root@rocky8 ~]# du /mnt/sdb1
8	/mnt/sdb1
#创建一个新文件又占用了4k

[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 #块大小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 挂载
[root@rocky8 ~]# ls /mnt/sdb1
lost+found
#挂载之后原来的数据就看不见了,原来的数据被隐藏了

[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 #已经占用2821的磁盘空间

[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 #新建文件增加了1k 空间

[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
#卸载了分区挂载,就可以看到原来根分区上的数据

#作为挂载点文件夹,第一文件夹必须存在,第二这个文件夹应该是一个空文件夹

[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
#只要挂载了分区,用df才能看的见

[root@rocky8 ~]# ls /mnt/sdb2
sdb1  sdb2
#xfs文件系统,比ext4元数据占用的空间要大

[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 默认查看的是以1k 为单位的

[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  也可以查看挂载信息

[root@rocky8 ~]# mount /dev/sdb1 /mnt/sdb2
[root@rocky8 ~]# ls /mnt/sdb2
a.txt  b.txt  c.txt  lost+found
#一个目录 只能挂载一个分区,如果挂载多个分区,原来挂载的分区,里边的文件就被隐藏了,除非卸载现在挂载的分区才能看到

[root@rocky8 ~]# umount /mnt/sdb2
[root@rocky8 ~]# ls /mnt/sdb2
sdb1  sdb2  x.txt  y.txt
#卸载了,原来的又回来了

[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
#一个分区可以挂载多个挂载点,但是它里边的数据是一样的

[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 延迟更新读时间,当读时间达到一天以上才更新,或者读时间,比写时间旧的时候才更新,只有追加时,只是修改了文件,没有读文件,才会出现读时间比修改时间早,只有这个时候才会更新读时间

#可以在挂载的时候加上noatime,nodiratime,它就不会去更新读时间,但是如果touch文件它还是会更新读时间

[root@rocky8 ~]# touch /mnt/sdb2/xx.txt
[root@rocky8 ~]# cd /mnt/sdb2
#如果有人正在访问目录
[root@rocky8 sdb2]# umount /mnt/sdb2
umount: /mnt/sdb2: target is busy.
#现在是不能卸载挂载的分区的

[root@rocky8 sdb2]# fuser -v /mnt/sdb2 #fuser -v  查看谁正在访问此目录
                     USER        PID ACCESS COMMAND
/mnt/sdb2:           root     kernel mount /mnt
                     root        917 ..c.. bash

[root@rocky8 sdb2]# fuser -mk /mnt/sdb2 #fuser -mk  可以强行踢掉使用此目录的用户
/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 ~]# 
#踢了访问的用户就会退出登录

[root@rocky8 ~]# fuser -v /mnt/sdb2
                     USER        PID ACCESS COMMAND
/mnt/sdb2:           root     kernel mount /mnt
#现在就没有人访问了

[root@rocky8 ~]# umount /mnt/sdb2
#现在取消挂载就可以了

[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
#用mount -o remount 重新挂载,不用踢正在访问的用户

[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) #这里已经是ro 只读

[root@rocky8 ~]# touch /mnt/sdb2/yy.txt
touch: cannot touch '/mnt/sdb2/yy.txt': Read-only file system
#现在就不能往里写文件了

[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.
#/ 根分区是不能取消挂载的

[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  查看挂载情况

[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
#添加下面内容
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)
#现在/dev/sdb1是没有挂载的

[root@rocky8 ~]# mount -a #mount -a  立即挂载
[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)
#现在/dev/sdb1已经挂载了

[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
#由于是只读挂载,现在是不能删除里边的文件的

[root@rocky8 sdb1]# vim /etc/fstab
UUID=f7d5345f-5f29-417d-a044-37508852e80f /mnt/sdb1              ext4     noatime,nodiratime  0 0
#删了ro,默认就是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 是不能立即生效的

[root@rocky8 sdb1]# mount -o remount /dev/sdb1 #必须要remount重新挂载

[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)
#现在就生效了

#mount -a  是如果从来没有在/etc/fstab存在的,新加的是立即生效的,如果已经存在,改的是不能立即生效的

[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
#现在就可以删除里边的文件或文件夹了,lost+found文件夹,是ext2、 ext3、etx4的特性,相当于收容所

[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是不修改的

[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: -
#强行touch 了,atime是修改的

[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
#重启之后,/dev/sdb1是自动挂载的

[root@rocky8 ~]# vim /etc/fstab
UUID=f7d5345f-5f29-417d-a044-37508852e800 /mnt/sdb1              ext4     noatime,nodiratime  0 0
#假如在设置时候把UUID 写错了,系统重启后是不能正常启动的

[root@rocky8 ~]# reboot

在这里插入图片描述
#会进入故障状态,输入root密码

在这里插入图片描述
#查看/dev/sdb1 是没有挂载的

在这里插入图片描述
#进入配置文件

在这里插入图片描述
#把报错的磁盘挂载那行先注释掉

在这里插入图片描述
#重启

在这里插入图片描述
#现在系统就能正常启动了

[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

范例:centos7, 8 /etc/fstab 的分区UUID错误,无法启动

自动进入emergency mode,输入root 密码
#cat /proc/mounts 可以查看到/ 以rw方式挂载
#vim /etc/fstab
#reboot

范例:centos 6 /etc/fstab 的分区UUID错误,无法启动

#如果/etc/fstab 的挂载设备出错,比如文件系统故障,并且文件系统检测项(即第6项为非0),将导致无法启动

#自动进入emergency mode,输入root 密码
#cat /proc/mounts 可以查看到/ 以ro方式挂载,无法直接修改配置文件
#mount -o remount,rw /
#vim /etc/fstab
#将故障行的最后1项,即第6项修改为0,开机不检测此项挂载设备的健康性,从而忽略错误,能实现启动

范例:/etc/fstab格式

[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 处理交换文件和分区

2.4.1 swap 介绍

swap交换分区是系统RAM的补充,swap 分区支持虚拟内存。当没有足够的 RAM 保存系统处理的数据时会将数据写入 swap 分区,当系统缺乏 swap 空间时,内核会因 RAM 内存耗尽而终止进程。配置过多 swap 空间会造成存储设备处于分配状态但闲置,造成浪费,过多 swap 空间还会掩盖内存泄露

注意:为优化性能,可以将swap 分布存放,或高性能磁盘存放

官方推荐推荐系统 swap 空间

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

系统中的 RAM 量推荐的 swap 空间允许休眠的建议 swap 空间大小
低于 2 GBRAM 量的2倍数RAM 容量的三倍
2 GB - 8 GB等于 RAM 量RAM 量的倍数
8 GB - 64 GB4 GB 到 RAM 容量的 0.5 倍RAM 容量的 1.5 倍
超过 64 GB独立负载(至少 4GB)不建议使用休眠功能

范例:

[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
#如果内存被占满,没有虚拟内存的时候,会出现OOM报错,OOM 就是 out of memory,内存满了

[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)
#立即使用8G内存,会报内存不足

[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 #把/dev/sdb5改成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 创建swap分区
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 #立即生效
[root@rocky8 ~]# swapon -s #查看swap情况
Filename				Type		Size	Used	Priority
/dev/sda5                              	partition	2097148	0	-2
/dev/sdb5                              	partition	2097148	0	-3
#-2 ,-3 是优先级,数字越小优先级越高,优先使用

[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 增加2G

#删除swap 要保证被删除的分区,没有被使用

[root@rocky8 ~]# vim /etc/fstab
UUID=9a3b3cde-e94d-4f62-9c7e-069d2e3e400b swap                    swap    pri=100         0 0
#pre=100  就是设置优先级,设置的正数优先级,高于系统默认的负数优先级

[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

#删除swap
[root@rocky8 ~]# swapoff /dev/sdb5 #先关闭/dev/sdb5,swap

[root@rocky8 ~]# vim /etc/fstab
#删除下面内容
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.
#删除分区

[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 #把/dev/sda5正在使用的挪走
[root@rocky8 ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:          782Mi       179Mi       336Mi       5.0Mi       266Mi       468Mi
Swap:            0B          0B          0B
#现在内存使用变大,swap分区没有了

2.4.2 交换分区实现过程

  1. 创建交换分区或者文件
  2. 使用mkswap写入特殊签名
  3. 在/etc/fstab文件中添加适当的条目
  4. 使用swapon -a 激活交换空间

启用swap分区

swapon [OPTION]... [DEVICE]

选项:

-a:激活所有的交换分区
-p PRIORITY:指定优先级,也可在/etc/fstab 在第4列指定:pri=value

范例:创建swap分区

[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

禁用swap分区:

swapoff [OPTION]... [DEVICE]

范例:禁用swap分区

[root@rocky8 ~]# sed -i.bak '/swap/d' /etc/fstab
[root@rocky8 ~]# swapoff -a

SWAP的优先级
可以指定swap分区0到32767的优先级,值越大优先级越高

如果用户没有指定,那么核心会自动给swap指定一个优先级,这个优先级从-1开始,每加入一个新的没有用户指定优先级的swap,会给这个优先级减一

先添加的swap的缺省优先级比较高,除非用户自己指定一个优先级,而用户指定的优先级(是正数)永远高于核心缺省指定的优先级(是负数)

2.4.3 swap的使用策略

/proc/sys/vm/swappiness 的值决定了当内存占用达到一定的百分比时,会启用swap分区的空间

范例:

[root@centos8 ~]# cat /proc/sys/vm/swappiness
30
[root@rhel5 ~]# cat /proc/sys/vm/swappiness
60

说明:内存在使用到100-30=70%的时候,就开始出现有交换分区的使用。简单地说这个参数定义了系统对swap的使用倾向,默认值为30,值越大表示越倾向于使用swap。可以设为0,这样做并不会禁止对swap的使用,只是最大限度地降低了使用swap的可能性

范例:

[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 磁盘常见工具

2.5.1 文件系统空间占用等信息的查看工具df

df [OPTION]... [FILE]...

常用选项

-H 以10为单位
-T 文件系统类型
-h human-readable
-i inodes instead of blocks
-P 以Posix兼容的格式输出

范例:

[[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 显示文件系统
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

范例:

[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 查看某目录总体空间占用状态du

du [OPTION]... DIR

常用选项

-h human-readable
-s summary
    --max-depth=# 指定最大目录层级
    -x, --one-file-system #忽略不在同一个文件系统的目录

范例:

[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  只显示/data目录信息

2.5.3 工具dd

dd 命令:convert and copy a file

格式:

dd if=/PATH/FROM/SRC of=/PATH/TO/DEST bs=# count=#

常用选项

if=file 从所命名文件读取而不是从标准输入
of=file 写到所命名的文件而不是到标准输出
bs=size block size, 指定块大小(既是是ibs也是obs)
cbs=size 一次转化size个byte
skip=blocks 从开头忽略blocks个ibs大小的块
seek=blocks 从开头忽略blocks个obs大小的块
count=n 复制n个bs
conv=conversion[,conversion...] 用指定的参数转换文件

conversion 转换参数:
ascii 转换 EBCDIC 为 ASCII
ebcdic 转换 ASCII 为 EBCDIC
lcase 把大写字符转换为小写字符
ucase 把小写字符转换为大写字符
nocreat 不创建输出文件
noerror 出错时不停止
notrunc 不截短输出文件
sync 把每个输入块填充到ibs个字节,不足部分用空(NUL)字符补齐
fdatasync 写完成前,物理写入输出文件

范例:

#skip  是从if 目标输入时,跳过多少个
#seek  是从of 目标输出时,跳过多少个

[root@rocky8 ~]# dd of=/data/a.txt conv=ucase #转换大小写
abc
xyz
0+2 records in
0+1 records out
8 bytes copied, 24.516 s, 0.0 kB/s
#ctrl+d  结束
[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每次读1个字节,count=2读2次,skip=3 从f1.txt跳过3个,seek=4从f2.txt跳过4个, 输出到f2.txt,f1.txt的最后f被截断了,f2.txt的789也被截断了,所以就没有了,最后结果就是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  这就是不截断

[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
#创建的是一个稀疏文件,或者叫空洞文件

范例:

#备份MBR
dd if=/dev/sda of=/tmp/mbr.bak bs=512 count=1
#破坏MBR中的bootloader
dd if=/dev/zero of=/dev/sda bs=64 count=1 seek=446

2.6 练习

1、创建一个2G的文件系统,块大小为2048byte,预留1%可用空间,文件系统ext4,卷标为TEST,要求此分区开机后自动挂载至/test目录,且默认有acl挂载选项
2、写一个脚本,完成如下功能:
(1) 列出当前系统识别到的所有磁盘设备
(2) 如磁盘数量为1,则显示其空间使用信息
否则,则显示最后一个磁盘上的空间使用信息
3、将CentOS6的CentOS-6.10-x86_64-bin-DVD1.iso和CentOS-6.10-x86_64-bin-DVD2.iso两个文件,合并成一个CentOS-6.10-x86_64-Everything.iso文件,并将其配置为yum源

标签:relatime,rw,33,文件系统,dev,sys,cgroup,磁盘,type
来源: https://blog.csdn.net/qq_25599925/article/details/120870068