Linux基础实践

原创

njsummer 2021-12-05 00:40:53 ©著作权

©著作权归作者所有：来自51CTO博客作者njsummer的原创作品，请联系作者获取转载授权，否则将追究法律责任

1、统计出/etc/passwd文件中其默认shell为非/sbin/nologin的用户个数，并将用户都显示出来

## 用命令 grep "/sbin/nologin" /etc/passwd 列出包含/sbin/nologin的行，并显示
[root@centos8301]# grep  "/sbin/nologin" /etc/passwd   
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
systemd-coredump:x:999:997:systemd Core Dumper:/:/sbin/nologin
systemd-resolve:x:193:193:systemd Resolver:/:/sbin/nologin
tss:x:59:59:Account used for TPM access:/dev/null:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
geoclue:x:997:995:User for geoclue:/var/lib/geoclue:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pipewire:x:996:992:PipeWire System Daemon:/var/run/pipewire:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
libstoragemgmt:x:995:989:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
unbound:x:994:988:Unbound DNS resolver:/etc/unbound:/sbin/nologin
gluster:x:993:987:GlusterFS daemons:/run/gluster:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
saslauth:x:992:76:Saslauthd user:/run/saslauthd:/sbin/nologin
dnsmasq:x:985:985:Dnsmasq DHCP and DNS server:/var/lib/dnsmasq:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
sssd:x:984:984:User for sssd:/:/sbin/nologin
cockpit-ws:x:983:982:User for cockpit web service:/nonexisting:/sbin/nologin
cockpit-wsinstance:x:982:981:User for cockpit-ws instances:/nonexisting:/sbin/nologin
chrony:x:981:980::/var/lib/chrony:/sbin/nologin
colord:x:980:979:User for colord:/var/lib/colord:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
setroubleshoot:x:979:978::/var/lib/setroubleshoot:/sbin/nologin
flatpak:x:978:977:User for flatpak system helper:/:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
clevis:x:977:976:Clevis Decryption Framework unprivileged user:/var/cache/clevis:/sbin/nologin
gnome-initial-setup:x:976:975::/run/gnome-initial-setup/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
slackware:x:2002:2019::/home/slackware:/sbin/nologin
[root@centos8301]# 

##用 -v, --invert-match ,查出不包含/sbin/nologin的行，并输出
[root@centos8301]# grep -v "/sbin/nologin" /etc/passwd
root:x:0:0:root:/root:/bin/bash
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
summer:x:1000:1000:summer:/home/summer:/bin/bash
mageia:x:1100:1100::/home/linux:/bin/bash
user1:x:2003:2003::/home/user1:/bin/bash
user2:x:2004:2004::/home/user2:/bin/bash
user3:x:2005:2005::/home/user3:/bin/bash
sabrina:x:2006:2006::/home/sabrina:/bin/bash
mage:x:2007:2007::/home/mage:/bin/bash
[root@centos8301]# 

## 用cut命令以:分号为分隔符，取第1列，即用户名
[root@centos8301]# grep -v "/sbin/nologin" /etc/passwd | cut -d: -f1
root
sync
shutdown
halt
summer
mageia
user1
user2
user3
sabrina
mage
[root@centos8301]#

2、查出用户UID最大值的用户名、UID及shell类型

[root@centos8301]# cat /etc/passwd | sort -t: -k3 -n | tail -1 | cut -d: -f1,3,7
nobody:65534:/sbin/nologin
[root@centos8301]# 

[root@centos8301]# getent passwd | sort -t: -k3 -n | tail -1 | cut -d: -f1,3,7
nobody:65534:/sbin/nologin
[root@centos8301]#

##思路：
1.只有在passwd才能查到UID、用户名及shell类型，命令：getent passwd 或 cat /etc/passwd
2.对UID先排序，用sort，以:为分隔符分列 -t:，对第3列UID -k3，数字排序 -n
3.tail -1取出UID最大值的UID
4.用cut分别把第1列用户名、第3列UID、第7列shell类型列出来

## cat命令先查出 /etc/passwd 文件的第1/3/7列的内容，以：为分隔符
[root@centos8301]# cat /etc/passwd  | cut -d: -f1,3,7
root:0:/bin/bash
bin:1:/sbin/nologin
daemon:2:/sbin/nologin
adm:3:/sbin/nologin
lp:4:/sbin/nologin
sync:5:/bin/sync
shutdown:6:/sbin/shutdown
halt:7:/sbin/halt
mail:8:/sbin/nologin
operator:11:/sbin/nologin
games:12:/sbin/nologin
ftp:14:/sbin/nologin
nobody:65534:/sbin/nologin
dbus:81:/sbin/nologin
systemd-coredump:999:/sbin/nologin
systemd-resolve:193:/sbin/nologin
tss:59:/sbin/nologin
polkitd:998:/sbin/nologin
geoclue:997:/sbin/nologin
rtkit:172:/sbin/nologin
pipewire:996:/sbin/nologin
pulse:171:/sbin/nologin
libstoragemgmt:995:/sbin/nologin
qemu:107:/sbin/nologin
usbmuxd:113:/sbin/nologin
unbound:994:/sbin/nologin
gluster:993:/sbin/nologin
rpc:32:/sbin/nologin
avahi:70:/sbin/nologin
saslauth:992:/sbin/nologin
dnsmasq:985:/sbin/nologin
radvd:75:/sbin/nologin
sssd:984:/sbin/nologin
cockpit-ws:983:/sbin/nologin
cockpit-wsinstance:982:/sbin/nologin
chrony:981:/sbin/nologin
colord:980:/sbin/nologin
rpcuser:29:/sbin/nologin
setroubleshoot:979:/sbin/nologin
flatpak:978:/sbin/nologin
gdm:42:/sbin/nologin
clevis:977:/sbin/nologin
gnome-initial-setup:976:/sbin/nologin
sshd:74:/sbin/nologin
tcpdump:72:/sbin/nologin
summer:1000:/bin/bash
postfix:89:/sbin/nologin
mageia:1100:/bin/bash
slackware:2002:/sbin/nologin
user1:2003:/bin/bash
user2:2004:/bin/bash
user3:2005:/bin/bash
sabrina:2006:/bin/bash
mage:2007:/bin/bash

##sort 命令对UID进行排序
[root@centos8301]# cat /etc/passwd  | cut -d: -f1,3,7 | sort -t: -k2 -n
root:0:/bin/bash
bin:1:/sbin/nologin
daemon:2:/sbin/nologin
adm:3:/sbin/nologin
lp:4:/sbin/nologin
sync:5:/bin/sync
shutdown:6:/sbin/shutdown
halt:7:/sbin/halt
mail:8:/sbin/nologin
operator:11:/sbin/nologin
games:12:/sbin/nologin
ftp:14:/sbin/nologin
rpcuser:29:/sbin/nologin
rpc:32:/sbin/nologin
gdm:42:/sbin/nologin
tss:59:/sbin/nologin
avahi:70:/sbin/nologin
tcpdump:72:/sbin/nologin
sshd:74:/sbin/nologin
radvd:75:/sbin/nologin
dbus:81:/sbin/nologin
postfix:89:/sbin/nologin
qemu:107:/sbin/nologin
usbmuxd:113:/sbin/nologin
pulse:171:/sbin/nologin
rtkit:172:/sbin/nologin
systemd-resolve:193:/sbin/nologin
gnome-initial-setup:976:/sbin/nologin
clevis:977:/sbin/nologin
flatpak:978:/sbin/nologin
setroubleshoot:979:/sbin/nologin
colord:980:/sbin/nologin
chrony:981:/sbin/nologin
cockpit-wsinstance:982:/sbin/nologin
cockpit-ws:983:/sbin/nologin
sssd:984:/sbin/nologin
dnsmasq:985:/sbin/nologin
saslauth:992:/sbin/nologin
gluster:993:/sbin/nologin
unbound:994:/sbin/nologin
libstoragemgmt:995:/sbin/nologin
pipewire:996:/sbin/nologin
geoclue:997:/sbin/nologin
polkitd:998:/sbin/nologin
systemd-coredump:999:/sbin/nologin
summer:1000:/bin/bash
mageia:1100:/bin/bash
slackware:2002:/sbin/nologin
user1:2003:/bin/bash
user2:2004:/bin/bash
user3:2005:/bin/bash
sabrina:2006:/bin/bash
mage:2007:/bin/bash
nobody:65534:/sbin/nologin
[root@centos8301]# 

##tail取出最后一行，即为UID最大
[root@centos8301]# cat /etc/passwd  | cut -d: -f1,3,7 | sort -t: -k2 -n | tail -n1
nobody:65534:/sbin/nologin

## 其他命令摘录
[root@centos8301]# cat /etc/passwd | cut -d: -f3 | sort -rn | head -1
65534
[root@centos8301]# grep `cat /etc/passwd | cut -d: -f3 | sort -rn | head -1` /etc/passwd | cut -d: -f1,3,7
nobody:65534:/sbin/nologin
[root@centos8301]# 

[root@centos8301]# cat /etc/passwd | grep 65534
nobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin
[root@centos8301]# cat /etc/passwd | awk -F':' -v u="" -v maxid=0 '{ if($3>maxid) {maxid=$3;u=$1"--"$3"--"$7} } END{print u}'
nobody--65534--/sbin/nologin
[root@centos8301]#

[root@centos8301]# vim max-uid.sh     
#!/bin/bash
uid=`cat /etc/passwd |cut -d ":" -f3`
max=0   # 这个赋值必须放在for循环体的外面，否则就只能查到最后一个UID值
for i in $uid;do
    if [ $i -gt $max ]
      then  max=$i
    fi
done
grep $max /etc/passwd |cut -d ":" -f1,3,7
[root@centos8301]# 

#赋予可执行权限
[root@centos8301]# chmod 755 max-uid.sh

#运行脚本，得到结果
[root@centos8301]# bash max-uid.sh
nobody:65534:/sbin/nologin
[root@centos8301]#

3、统计当前连接本机的每个远程主机IP的连接数，并按从大到小排序

[root@centos8301]# ss -tnH
ESTAB          0             96         192.168.250.101:22         192.168.250.250:61082        
ESTAB          0             0          192.168.250.101:22         192.168.250.250:61198        
ESTAB          0             0          192.168.250.101:22         10.0.96.253:56072        
CLOSE-WAIT     32            0          192.168.250.101:59714      8.43.85.13:443          
ESTAB          0             0          192.168.250.101:22         192.168.250.201:48570        
[root@centos8301]# ss -tnH  | awk -F' +|:' '{print $6}' | sort | uniq -c | sort -nr
      2 192.168.250.250
      1 8.43.85.13
      1 192.168.250.201
      1 10.0.96.253
[root@centos8301]#

[root@centos8301-shone-cn ~]# ss -tnH
ESTAB          0                0         192.168.250.101:22        192.168.250.250:61275       
ESTAB          0                96        192.168.250.101:22        10.0.96.253:56893             
ESTAB          0                0         192.168.250.101:22        192.168.250.250:61361             
ESTAB          0                0         192.168.250.101:22        192.168.250.250:61359             
ESTAB          0                0         192.168.250.101:22        192.168.250.250:61360             
[root@centos8301-shone-cn ~]# ss -tnH  | awk -F' +|:' '{print $6}' | sort | uniq -c | sort -nr
      4 192.168.250.250
      1 10.0.96.253
[root@centos8301-shone-cn ~]#

[root@centos8301]#  netstat -nt | grep "tcp"|tr -s " " ":"|cut -d: -f6 |sort |uniq -c
      1 10.0.96.253
      4 192.168.250.250
[root@centos8301]#

4、编写脚本disk.sh，显示当前硬盘分区中空间利用率最大的值

## 脚本编写  可以定义一个 .vimrc 文件用于vim的统一格式，放在/home/xxx目录下面供自己使用
[root@centos8301]# vim disk.sh
#!/bin/bash
#
#********************************************************************
#Author:                    Wu-Dong-Wu-Xia
#QQ:                        XXXXXXXXXX
#Date:                      2021-12-05
#FileName：                 disk.sh
#URL:                       http://www.XXXX.cn
#Description：          The test script
#Copyright (C):         2021 All rights reserved
#********************************************************************
MAX_SPACE_OCCUPY=$(df -lh | grep / | tr -s ' ' '%' |cut -d"%" -f5 | sort -nr | head -n 1)
echo Disk-Space utilization-MAX=$MAX_SPACE_OCCUPY% 
[root@centos8301]# 
# 脚本的解读
# dh -lh 获取易读的磁盘分区信息
# grep / 将第一行过滤掉
# tr -s ' ' '%' 将连续的空格" "替换为百分号"%"
# cut 以百分号"%"作为分隔符，取出第5列，即空间利用率
# sort -nr 对空间利用率按数字从大到小排序
# head 取出第一行，即空间利用率最大的值


## 列出磁盘信息，用于比对结果
[root@centos8301-shone-cn ~]# df -lh
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        1.8G     0  1.8G   0% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
tmpfs           1.9G  9.3M  1.9G   1% /run
tmpfs           1.9G     0  1.9G   0% /sys/fs/cgroup
/dev/sda2       100G  6.0G   94G   6% /
/dev/sda1       200M  7.3M  193M   4% /boot/efi
/dev/sda4        50G  390M   50G   1% /data
tmpfs           374M  1.2M  373M   1% /run/user/42
tmpfs           374M     0  374M   0% /run/user/0
[root@centos8301-shone-cn ~]# 

## 赋予脚本文件的执行权限
[root@centos8301]# chmod 755 disk.sh
[root@centos8301]# ll  disk.sh
-rwxr-xr-x. 1 root root 506 Dec  5 23:22 disk.sh
[root@centos8301]# 

## 在bash下运行 disk.sh 脚本
[root@centos8301]# bash disk.sh
6
[root@centos8301]#

##验证脚本的信息
[root@centos8301]# cat disk.sh
#!/bin/bash
#
#********************************************************************
#Author:                    Wu-Dong-Wu-Xia
#QQ:                        1050572574
#Date:                      2021-12-05
#FileName：                 disk.sh
#URL:                       http://www.shone.cn
#Description：          The test script
#Copyright (C):         2021 All rights reserved
#********************************************************************
MAX_SPACE_OCCUPY=$(df -h | grep / | tr -s ' ' '%' |cut -d"%" -f5 | sort -nr | head -n 1)
echo Disk-Space utilization-MAX=$MAX_SPACE_OCCUPY% 
[root@centos8301]#

5、编写脚本 systeminfo.sh，显示当前主机系统信息，包括:主机名，IPv4地址，操作系统版本，内核版本，CPU型号，内存大小，硬盘大小

## 编写脚本
[root@centos8301-shone-cn ~]# vim systeminfo.sh 
[root@centos8301-shone-cn ~]# cat systeminfo.sh 
#!/bin/bash
#
############################################################################
#Author:                    Wu-Dong-Wu-Xia
#QQ:                        XXXXXXXXXXX
#Date:                      2021-12-05
#FileName：                 systeminfo.sh
#URL:                       http://www.XXXXX.cn
#Description：          The test script
#Copyright (C):         2021 All rights reserved
############################################################################

BLUE="\e[34m"
END="\e[0m"
WIDTH=90
MID=$(($WIDTH / 2))
SEPAR_RECORD=$( for i in `seq 1 $WIDTH`;do echo -n "-";done)
SEPAR_FILE="|"
MID_SEPAR="\033[${MID}G${SEPAR_FILE}"
LEFT_SEPAR="\033[1G${SEPAR_FILE}"
RIGHT_SEPAR="\033[${WIDTH}G${SEPAR_FILE}"


HOST=$(hostname)
IP=$(ip a  | grep 'global' | awk '{print $2}')
OS_VERSION=$(cat /etc/redhat-release)
KERNEL_VERSION=$(uname -r)
CPU_TYPE=$(cat /proc/cpuinfo  | grep 'model name' | cut -d":" -f2 | head -n 1)
MEMORY_SIZE=$(cat /proc/meminfo | grep 'MemTotal' | tr -s ' ' | cut -d":" -f2)
DISK_SIZE=$(lsblk | grep disk | tr -s ' ' | cut -d' ' --output-delimiter ":"  -f1,4)




echo $SEPAR_RECORD

# echo hostname
ATTR="hostname"
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
SKIP_VALUE=$(( MID/2 - ${#HOST}/2 + MID))
echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${HOST}${END}"
echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
echo $SEPAR_RECORD

# echo IP
ATTR="IP"
IP_NUM=$( echo $IP | awk "END{print NF}")
LINE=1
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
for i in $IP;do
    SKIP_VALUE=$(( MID/2 - ${#i}/2 + MID))
    if (( LINE==(IP_NUM + 1)/2 ));then
            echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
    fi
    (( LINE++ ))
    echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${i}${END}" 
    echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
    
done
echo $SEPAR_RECORD


# echo os version
ATTR="os version"
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
SKIP_VALUE=$(( MID/2 - ${#OS_VERSION}/2 + MID))
echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${OS_VERSION}${END}"
echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
echo $SEPAR_RECORD


# echo kernel version
ATTR="kernel version"
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
SKIP_VALUE=$(( MID/2 - ${#KERNEL_VERSION}/2 + MID))
echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${KERNEL_VERSION}${END}"
echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
echo $SEPAR_RECORD

# echo cpu type
ATTR="cpu type"
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
SKIP_VALUE=$(( MID/2 - ${#CPU_TYPE}/2 + MID))
echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${CPU_TYPE}${END}"
echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
echo $SEPAR_RECORD

# echo memory size
ATTR="memory size"
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
SKIP_VALUE=$(( MID/2 - ${#MEMORY_SIZE}/2 + MID))
echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${MEMORY_SIZE}${END}"
echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
echo $SEPAR_RECORD


# echo disk size
ATTR="disk size"
DISK_NUM=$( echo $DISK_SIZE | awk "END{print NF}")
LINE=1
SKIP_ATTR=$(( MID/2 -${#ATTR}/2 ))
for i in $DISK_SIZE;do
    SKIP_VALUE=$(( MID/2 - ${#i}/2 + MID))
    if (( LINE==(DISK_NUM + 1)/2 ));then
            echo -en "\033[${SKIP_ATTR}G" && echo -en "${ATTR}"
    fi
    (( LINE++ ))
    echo -en "\033[${SKIP_VALUE}G" && echo -en "${BLUE}${i}${END}" 
    echo -e "${LEFT_SEPAR}${MID_SEPAR}${RIGHT_SEPAR}"
    
done
echo $SEPAR_RECORD

## 授予脚本的运行权限
[root@centos8301-shone-cn ~]# chmod 755 systeminfo.sh 

## 运行脚本
[root@centos8301-shone-cn ~]# bash systeminfo.sh
------------------------------------------------------------------------------------------
|                hostname                   |            centos8301-shone-cn             |
------------------------------------------------------------------------------------------
|                   IP                      |            192.168.250.101/24              |
|                                           |             192.168.122.1/24               |
------------------------------------------------------------------------------------------
|               os version                  |       CentOS Linux release 8.4.2105        |
------------------------------------------------------------------------------------------
|             kernel version                |         4.18.0-305.3.1.el8.x86_64          |
------------------------------------------------------------------------------------------
|                cpu type                   | Intel(R) Xeon(R) CPU E7-4809 v4 @ 2.10GHz  |
------------------------------------------------------------------------------------------
|               memory size                 |                 3825304 kB                 |
------------------------------------------------------------------------------------------
|                disk size                  |                 sda:200G                   |
------------------------------------------------------------------------------------------
[root@centos8301-shone-cn ~]#