[root@rhcsa ~]# sed 's/^[[:space:]]*//' /etc/grub2.cfg

2、删除/etc/fstab文件中所有以#开头，后面至少跟一个空白字符的行的行首的#和空白字符

[root@rhcsa ~]# sed 's/^#[[:space:]]*//' /etc/fstab/etc/fstab
Created by anaconda on Fri Jun  3 10:02:33 2022Accessible filesystems, by reference, are maintained under '/dev/disk'
See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=6e5263a8-9127-4657-a83b-dff790e2a139 /boot                   xfs     defaults        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
[root@rhcsa ~]#

3、在 grub2.cfg每一行行首增加#号

[root@rhcsa ~]# sed 's/^.*$/#&/' grub2.cfg

4、在/etc/fstab文件中不以#开头的行的行首增加#号

[root@rhcsa ~]# sed 's/^[^#]/#&/' /etc/fstab#
# /etc/fstab
# Created by anaconda on Fri Jun  3 10:02:33 2022
#
# 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
#
#/dev/mapper/centos-root /                       xfs     defaults        0 0
#UUID=6e5263a8-9127-4657-a83b-dff790e2a139 /boot                   xfs     defaults        0 0
#/dev/mapper/centos-swap swap                    swap    defaults        0 0
[root@rhcsa ~]#

5、利用sed 取出ifconfig命令中本机的IPv4地址

方法一：
[root@rhcsa ~]# ifconfig | sed -n '2p' | sed 's/^.*[[:space:]]*inet.*[[:space:]]//'
192.168.188.255
[root@rhcsa ~]#

方法二：
[root@rhcsa ~]# ifconfig | sed -n '2p' | sed 's/^.*[[:space:]]*inet//' | sed 's/[[:space:]]*netmask.*//'192.168.188.128
[root@rhcsa ~]# 

6、关闭本机SELinux的功能

[root@rhcsa ~]# vim /etc/sysconfig/selinux
Error detected while processing /root/.vimrc:
line    1:
E492: Not an editor command: [root@ scripts]# cat  ~/.vimrc
Press ENTER or type command to continue
[root@rhcsa ~]# cat /etc/sysconfig/selinux# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enable
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted[root@rhcsa ~]#

使用sed改变状态：

[root@rhcsa ~]# sed -i 's/enable/disabled/' /etc/sysconfig/selinux
[root@rhcsa ~]# cat /etc/sysconfig/selinux# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted[root@rhcsa ~]#

也可以这样修改：

[root@rhcsa ~]# sed -i 's/SELINUX=disabled/SELINUX=enable/' /etc/sysconfig/selinux
[root@rhcsa ~]# cat /etc/sysconfig/selinux# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enable
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

[root@rhcsa ~]# sed '7 c\SELINUX=enable' /etc/sysconfig/selinux# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enable
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted[root@rhcsa ~]#