How to run commands on a remote Linux system via SSH

Sometimes we may need to run some commands on a remote machine. If this is an occasional operation, you can log in to the remote system and execute commands directly to achieve this goal. But it gets annoying to do this every time. In this case, is there a better solution to get rid of this troublesome operation?

Yes, you can perform these operations from your local system without logging into the remote system. Is there any benefit to this? Without a doubt. This will save you a lot of good time.

How is this achieved? SSH allows you to run commands on a remote computer without logging into it.

The general syntax is as follows:

$ ssh [username]@[remote hostname or IP] [command or script]

1) How to run commands on a remote Linux system via SSH

The following example allows the user to run the df command on a remote Linux machine via ssh.

$ ssh [email protected] 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) How to run multiple commands on a remote Linux system via SSH

The following example allows the user to run multiple commands at once on a remote Linux machine via ssh.

Run the uptime command and the free command simultaneously on the remote Linux system.

$ ssh [email protected] "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) How to run commands with sudo privileges on a remote Linux system via SSH

The following example allows the user to run the fdisk command with sudo privileges on a remote Linux machine via ssh.

Ordinary users are not allowed to execute commands provided in the system binary (/usr/sbin/) directory. Users need root privileges to run it.

So you need root privileges to run the fdisk command on your Linux system. The which command returns the full executable path for a given command.

$ which fdisk
 /usr/sbin/fdisk
$ ssh -t [email protected] "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) How to run service control commands with sudo privileges on a remote Linux system via SSH

The following example allows the user to run service control commands with sudo privileges on a remote Linux machine via ssh.

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

5) How to run commands on a remote Linux system via SSH over a non-standard port

The following example allows the user to run the hostnamectl command on a remote Linux machine using a non-standard port via ssh.

$ ssh -p 2200 [email protected] 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) How to save the output of the remote system to the local system

The following example allows the user to run the top command on a remote Linux machine via ssh and save the output to the local system.

$ ssh [email protected] "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]

Alternatively, you can use the following format to run multiple commands on the remote system:

$ ssh [email protected] << EOF
hostnamectl
free -m
grep daygeek /etc/passwd
EOF

The output of the above command is as follows:

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) How to Run Local Bash Scripts on Remote Systems

The following example allows the user to run the local bash script remote-test.sh on a remote Linux machine via ssh.

Create a shell script and execute it.

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

The output of the above command is as follows:

$ ssh [email protected] '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

Alternatively, you can use pipes. If you think the output is not pretty, make some modifications to make it more elegant.

$ 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 "------------------------------------------------------------------"

The output of the above script is as follows:

$ cat /tmp/remote-test.sh | ssh [email protected]
 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) How to run multiple commands on multiple remote systems simultaneously

The following bash script allows the user to run multiple commands on multiple remote systems simultaneously. Implemented using a simple for loop.

To achieve this, you can try PSSH command or ClusterShell command or DSH command.

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

The output of the above script is as follows:

$ 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 [email protected] 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 [email protected] IDLE JCPU PCPU WHAT

9) How to add a password using sshpass command

If you find it troublesome to enter your password every time, I suggest you choose one of the following methods to solve this problem according to your needs.

If you perform similar operations frequently, I recommend setting up password-free authentication as it is a standard and permanent solution.

If you only perform these tasks a few times a month, I recommend using the sshpass tool. Just provide your password using the -p option.

$ sshpass -p 'Enter your password here' ssh -p 2200 [email protected] 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

Summarize

The above is the method I introduced to you to run commands on a remote Linux system through SSH. I hope it will be helpful to you. If you have any questions, please leave me a message and I will reply to you in time. I would also like to thank everyone for their support of the 123WORDPRESS.COM website!
If you find this article helpful, please feel free to reprint it and please indicate the source. Thank you!

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