Detailed explanation of SSH service (IV) -- local calling command of remote host
- The SSH server runs on ubuntu 18.04.1
- SSH client in Windows10
This section mainly explains that ssh calls commands on the remote host locally without logging in to the remote host shell
Application scenario:
- In the actual shell script writing process, you need to execute a command remotely through ssh, such as creating a new directory, etc
Implementation method:
ssh username@hostname command
SSH sends a command
Send the following command through Windows powershell
ssh tyustli@192.168.10.22 "ls"
Return result of command
cross-tool Desktop src temp test.c
Create a new directory
ssh tyustli@192.168.10.22 "mkdir tyustli;ls"
Return result of command
cross-tool Desktop src temp test.c tyustli
You can see that ssh returns the directory of the remote host by sending a command, but it is still under the powershell of windows
SSH sends multiple commands
ssh tyustli@192.168.10.22 "ls;pwd"
If you are sending multiple commands, the commands are separated by semicolons
SSH executes remote commands interactively
By specifying the - t parameter in the ssh command, you can interactively execute the remote command. In short, the executed command needs to stay in the shell of the remote host and wait for user interaction, that is, the interaction between remote shells,
By using the - t parameter, ssh keeps logging in to the remote host shell until the interactive command exits
top command without - t parameter:
tyustli@172.16.19.129 top TERM environment variable not set.
top command using the - t parameter
ssh -t tyustli@172.16.19.129 top
Execution results:
top - 00:43:30 up 2 days, 2:45, 2 users, load average: 0.00, 0.02, 0.00
Tasks: 379 total, 1 running, 294 sleeping, 0 stopped, 1 zombie
%Cpu(s): 0.1 us, 0.3 sy, 3.2 ni, 96.4 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 4002276 total, 815300 free, 1508844 used, 1678132 buff/cache
KiB Swap: 2097148 total, 2097148 free, 0 used. 2193032 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
67259 tyustli 20 0 51468 4236 3404 R 6.2 0.1 0:00.01 top
1 root 20 0 226204 9788 6700 S 0.0 0.2 0:11.33 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par_gp
6 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/0:0H-kb
9 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 mm_percpu_wq
10 root 20 0 0 0 0 S 0.0 0.0 0:00.22 ksoftirqd/0
11 root 20 0 0 0 0 I 0.0 0.0 1:51.00 rcu_sched
12 root rt 0 0 0 0 S 0.0 0.0 0:00.58 migration/0
13 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/0
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/0
15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/1
16 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/1
17 root rt 0 0 0 0 S 0.0 0.0 0:01.03 migration/1
18 root 20 0 0 0 0 S 0.0 0.0 0:00.32 ksoftirqd/1
20 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/1:0H-kb
21 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/2
22 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/2
23 root rt 0 0 0 0 S 0.0 0.0 0:01.05 migration/2
24 root 20 0 0 0 0 S 0.0 0.0 0:00.18 ksoftirqd/2
26 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/2:0H-kb
27 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/3
28 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_inject/3
29 root rt 0 0 0 0 S 0.0 0.0 0:01.02 migration/3
30 root 20 0 0 0 0 S 0.0 0.0 0:00.98 ksoftirqd/3
32 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/3:0H-kb
33 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs
34 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 netns
35 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_tasks_kthre
36 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kauditd
40 root 20 0 0 0 0 S 0.0 0.0 0:00.14 khungtaskd
41 root 20 0 0 0 0 S 0.0 0.0 0:00.00 oom_reaper
42 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 writeback
43 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kcompactd0
44 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
45 root 39 19 0 0 0 S 0.0 0.0 0:00.00 khugepaged
137 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kintegrityd
138 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kblockd
139 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 blkcg_punt_bio
140 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 tpm_dev_wq
141 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 ata_sff
142 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 md
When you issue an interactive command through Ctrl + C, you will be disconnected from the remote host
Through the above test, using the - t option, ssh will remain on the remote shell after issuing the command, waiting for the command execution to complete or waiting for the user to give subsequent commands. When the user sends Ctrl + C to exit the interactive command, he will disconnect from the remote shell and return to the local shell
Reference connection: https://www.cnblogs.com/chuanzhang053/p/8549122.html