如何通过 SSH 在远程 Linux 系统上运行命令

SSH 允许你无需登录到远程计算机就可以在它上面运行命令。

通用语法如下所示：

$ ssh [用户名]@[远程主机名或 IP] [命令或脚本]

1) 如何通过 SSH 在远程 Linux 系统上运行命令

下面的例子允许用户通过 ssh 在远程 Linux 机器上运行 df 命令。

$ ssh daygeek@CentOS7.2daygeek.com df -h
 
 Filesystem               Size  Used Avail Use% Mounted on
 /dev/mapper/centos-root   27G  4.4G   23G  17% /
 devtmpfs                 903M     0  903M   0% /dev
 tmpfs                    920M     0  920M   0% /dev/shm
 tmpfs                    920M  9.3M  910M   2% /run
 tmpfs                    920M     0  920M   0% /sys/fs/cgroup
 /dev/sda1               1014M  179M  836M  18% /boot
 tmpfs                    184M  8.0K  184M   1% /run/user/42
 tmpfs                    184M     0  184M   0% /run/user/1000

2) 如何通过 SSH 在远程 Linux 系统上运行多条命令

下面的例子允许用户通过 ssh 在远程 Linux 机器上一次运行多条命令。

同时在远程 Linux 系统上运行 uptime 命令和 free 命令。

$ ssh daygeek@CentOS7.2daygeek.com "uptime && free -m"
 
 23:05:10 up 10 min,  0 users,  load average: 0.00, 0.03, 0.03
 
              total       used       free     shared    buffers     cached
 Mem:          1878        432       1445          1        100        134
 -/+ buffers/cache:        197       1680
 Swap:         3071          0       3071

3) 如何通过 SSH 在远程 Linux 系统上运行带 sudo 权限的命令

下面的例子允许用户通过 ssh 在远程 Linux 机器上运行带有 sudo 权限的 fdisk 命令。

普通用户不允许执行系统二进制（/usr/sbin/）目录下提供的命令。用户需要 root 权限来运行它。

所以你需要 root 权限，好在 Linux 系统上运行 fdisk 命令。which 命令返回给定命令的完整可执行路径。

$ which fdisk
 /usr/sbin/fdisk

$ ssh -t daygeek@CentOS7.2daygeek.com "sudo fdisk -l"
 [sudo] password for daygeek:
 
 Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 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
 Disk label type: dos
 Disk identifier: 0x000bf685
 
 Device Boot      Start         End      Blocks   Id  System
 /dev/sda1   *        2048     2099199     1048576   83  Linux
 /dev/sda2         2099200    62914559    30407680   8e  Linux LVM
 
 Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 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
 
 Disk /dev/mapper/centos-root: 29.0 GB, 28982640640 bytes, 56606720 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
 
 Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304 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
 
 Connection to centos7.2daygeek.com closed.

4) 如何通过 SSH 在远程 Linux 系统上运行带 sudo 权限的服务控制命令

下面的例子允许用户通过 ssh 在远程 Linux 机器上运行带有 sudo 权限的服务控制命令。

$ ssh -t daygeek@CentOS7.2daygeek.com "sudo systemctl restart httpd"
 
 [sudo] password for daygeek:
 Connection to centos7.2daygeek.com closed.

5) 如何通过非标准端口 SSH 在远程 Linux 系统上运行命令

下面的例子允许用户通过 ssh 在使用了非标准端口的远程 Linux 机器上运行 hostnamectl 命令。

$ ssh -p 2200 daygeek@CentOS7.2daygeek.com hostnamectl
 
    Static hostname: Ubuntu18.2daygeek.com
          Icon name: computer-vm
            Chassis: vm
         Machine ID: 27f6c2febda84dc881f28fd145077187
            Boot ID: bbeccdf932be41ddb5deae9e5f15183d
     Virtualization: oracle
   Operating System: Ubuntu 18.04.2 LTS
             Kernel: Linux 4.15.0-60-generic
       Architecture: x86-64

6) 如何将远程系统的输出保存到本地系统

下面的例子允许用户通过 ssh 在远程 Linux 机器上运行 top 命令，并将输出保存到本地系统。

$ ssh daygeek@CentOS7.2daygeek.com "top -bc | head -n 35" > /tmp/top-output.txt

cat /tmp/top-output.txt
 
 top - 01:13:11 up 18 min,  1 user,  load average: 0.01, 0.05, 0.10
 Tasks: 168 total,   1 running, 167 sleeping,   0 stopped,   0 zombie
 %Cpu(s):  0.0 us,  6.2 sy,  0.0 ni, 93.8 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
 KiB Mem :  1882300 total,  1176324 free,   342392 used,   363584 buff/cache
 KiB Swap:  2097148 total,  2097148 free,        0 used.  1348140 avail Mem
 PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
  4943 daygeek   20   0  162052   2248   1612 R 10.0  0.1   0:00.07 top -bc
     1 root      20   0  128276   6936   4204 S  0.0  0.4   0:03.08 /usr/lib/sy+
     2 root      20   0       0      0      0 S  0.0  0.0   0:00.00 [kthreadd]
     3 root      20   0       0      0      0 S  0.0  0.0   0:00.25 [ksoftirqd/+
     4 root      20   0       0      0      0 S  0.0  0.0   0:00.00 [kworker/0:+
     5 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [kworker/0:+
     7 root      rt   0       0      0      0 S  0.0  0.0   0:00.00 [migration/+
     8 root      20   0       0      0      0 S  0.0  0.0   0:00.00 [rcu_bh]
     9 root      20   0       0      0      0 S  0.0  0.0   0:00.77 [rcu_sched]
    10 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [lru-add-dr+
    11 root      rt   0       0      0      0 S  0.0  0.0   0:00.01 [watchdog/0]
    13 root      20   0       0      0      0 S  0.0  0.0   0:00.00 [kdevtmpfs]
    14 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [netns]
    15 root      20   0       0      0      0 S  0.0  0.0   0:00.00 [khungtaskd]
    16 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [writeback]
    17 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [kintegrity+
    18 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [bioset]
    19 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [bioset]
    20 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 [bioset]

或者你也可以使用以下格式在远程系统上运行多条命令：

$ ssh daygeek@CentOS7.2daygeek.com << EOF
hostnamectl
free -m
grep daygeek /etc/passwd
EOF

上面命令的输出如下：

Pseudo-terminal will not be allocated because stdin is not a terminal.
    Static hostname: CentOS7.2daygeek.com
          Icon name: computer-vm
            Chassis: vm
         Machine ID: 002f47b82af248f5be1d67b67e03514c
            Boot ID: dca9a1ba06374d7d96678f9461752482
     Virtualization: kvm
   Operating System: CentOS Linux 7 (Core)
        CPE OS Name: cpe:/o:centos:centos:7
             Kernel: Linux 3.10.0-957.el7.x86_64
       Architecture: x86-64
 
               total        used        free      shared  buff/cache   available
 Mem:           1838         335        1146          11         355        1314
 Swap:          2047           0        2047
 
 daygeek:x:1000:1000:2daygeek:/home/daygeek:/bin/bash

7) 如何在远程系统上运行本地 Bash 脚本

下面的例子允许用户通过 ssh 在远程 Linux 机器上运行本地 bash 脚本 remote-test.sh。

创建一个 shell 脚本并执行它。

$ vi /tmp/remote-test.sh
 
#!/bin/bash
#Name: remote-test.sh
#--------------------
 uptime
 free -m
 df -h
 uname -a
 hostnamectl

上面命令的输出如下：

$ ssh daygeek@CentOS7.2daygeek.com 'bash -s' < /tmp/remote-test.sh
 
  01:17:09 up 22 min,  1 user,  load average: 0.00, 0.02, 0.08
 
               total        used        free      shared  buff/cache   available
 Mem:           1838         333        1148          11         355        1316
 Swap:          2047           0        2047
 
 Filesystem               Size  Used Avail Use% Mounted on
 /dev/mapper/centos-root   27G  4.4G   23G  17% /
 devtmpfs                 903M     0  903M   0% /dev
 tmpfs                    920M     0  920M   0% /dev/shm
 tmpfs                    920M  9.3M  910M   2% /run
 tmpfs                    920M     0  920M   0% /sys/fs/cgroup
 /dev/sda1               1014M  179M  836M  18% /boot
 tmpfs                    184M   12K  184M   1% /run/user/42
 tmpfs                    184M     0  184M   0% /run/user/1000
 
 Linux CentOS7.2daygeek.com 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
 
    Static hostname: CentOS7.2daygeek.com
          Icon name: computer-vm
            Chassis: vm
         Machine ID: 002f47b82af248f5be1d67b67e03514c
            Boot ID: dca9a1ba06374d7d96678f9461752482
     Virtualization: kvm
   Operating System: CentOS Linux 7 (Core)
        CPE OS Name: cpe:/o:centos:centos:7
             Kernel: Linux 3.10.0-957.el7.x86_64
       Architecture: x86-64

或者也可以使用管道。如果你觉得输出不太好看，再做点修改让它更优雅些。

$ vi /tmp/remote-test-1.sh
 
#!/bin/bash
#Name: remote-test.sh
 echo "---------System Uptime--------------------------------------------"
 uptime
 echo -e "\n"
 echo "---------Memory Usage---------------------------------------------"
 free -m
 echo -e "\n"
 echo "---------Disk Usage-----------------------------------------------"
 df -h
 echo -e "\n"
 echo "---------Kernel Version-------------------------------------------"
 uname -a
 echo -e "\n"
 echo "---------HostName Info--------------------------------------------"
 hostnamectl
 echo "------------------------------------------------------------------"

上面脚本的输出如下：

$ cat /tmp/remote-test.sh  | ssh daygeek@CentOS7.2daygeek.com
 Pseudo-terminal will not be allocated because stdin is not a terminal.
 ---------System Uptime--------------------------------------------
  03:14:09 up  2:19,  1 user,  load average: 0.00, 0.01, 0.05
 
 ---------Memory Usage---------------------------------------------
               total        used        free      shared  buff/cache   available
 Mem:           1838         376        1063          11         398        1253
 Swap:          2047           0        2047
 
 ---------Disk Usage-----------------------------------------------
 Filesystem               Size  Used Avail Use% Mounted on
 /dev/mapper/centos-root   27G  4.4G   23G  17% /
 devtmpfs                 903M     0  903M   0% /dev
 tmpfs                    920M     0  920M   0% /dev/shm
 tmpfs                    920M  9.3M  910M   2% /run
 tmpfs                    920M     0  920M   0% /sys/fs/cgroup
 /dev/sda1               1014M  179M  836M  18% /boot
 tmpfs                    184M   12K  184M   1% /run/user/42
 tmpfs                    184M     0  184M   0% /run/user/1000
 tmpfs                    184M     0  184M   0% /run/user/0
 
 ---------Kernel Version-------------------------------------------
 Linux CentOS7.2daygeek.com 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
 
 ---------HostName Info--------------------------------------------
    Static hostname: CentOS7.2daygeek.com
          Icon name: computer-vm
            Chassis: vm
         Machine ID: 002f47b82af248f5be1d67b67e03514c
            Boot ID: dca9a1ba06374d7d96678f9461752482
     Virtualization: kvm
   Operating System: CentOS Linux 7 (Core)
        CPE OS Name: cpe:/o:centos:centos:7
             Kernel: Linux 3.10.0-957.el7.x86_64
       Architecture: x86-64

8) 如何同时在多个远程系统上运行多条指令

下面的 bash 脚本允许用户同时在多个远程系统上运行多条指令。使用简单的 for 循环实现。

为了实现这个目的，你可以尝试 PSSH 命令或 ClusterShell 命令或 DSH 命令。

$ vi /tmp/multiple-host.sh
 
 for host in CentOS7.2daygeek.com CentOS6.2daygeek.com
 do
    ssh daygeek@${host} "uname -a;uptime;date;w"
 done

上面脚本的输出如下：

$ sh multiple-host.sh
 
 Linux CentOS7.2daygeek.com 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
 
  01:33:57 up 39 min,  1 user,  load average: 0.07, 0.06, 0.06
 
 Wed Sep 25 01:33:57 CDT 2019
 
  01:33:57 up 39 min,  1 user,  load average: 0.07, 0.06, 0.06
 USER     TTY      FROM             daygeek@CentOS7.2daygeek.com   IDLE   JCPU   PCPU WHAT
 daygeek  pts/0    192.168.1.6      01:08   23:25   0.06s  0.06s -bash
 
 Linux CentOS6.2daygeek.com 2.6.32-754.el6.x86_64 #1 SMP Tue Jun 19 21:26:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
 
  23:33:58 up 39 min,  0 users,  load average: 0.00, 0.00, 0.00
 
 Tue Sep 24 23:33:58 MST 2019
 
  23:33:58 up 39 min,  0 users,  load average: 0.00, 0.00, 0.00
 USER     TTY      FROM             daygeek@CentOS7.2daygeek.com   IDLE   JCPU   PCPU WHAT

9) 如何使用 sshpass 命令添加一个密码

如果你觉得每次输入密码很麻烦，我建议你视你的需求选择以下方法中的一项来解决这个问题。

如果你经常进行类似的操作，我建议你设置免密码认证，因为它是标准且永久的解决方案。

如果你一个月只是执行几次这些任务，我推荐你使用 sshpass 工具。只需要使用 -p 参数选项提供你的密码即可。

$ sshpass -p '在这里输入你的密码' ssh -p 2200 daygeek@CentOS7.2daygeek.com ip a
 
 1: lo:  mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
        valid_lft forever preferred_lft forever
     inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever
 2: eth0:  mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
     link/ether 08:00:27:18:90:7f brd ff:ff:ff:ff:ff:ff
     inet 192.168.1.12/24 brd 192.168.1.255 scope global dynamic eth0
        valid_lft 86145sec preferred_lft 86145sec
     inet6 fe80::a00:27ff:fe18:907f/64 scope link tentative dadfailed
        valid_lft forever preferred_lft forever

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