# Multiple sessions via single sshd? How?



## Bobi B. (Feb 14, 2019)

Today I've connected to a customer's server to handle an issue and I've noticed this:

```
1452  -  Is     0:00.01 |-- /usr/sbin/sshd
1854  -  Ss     0:01.16 | |-- sshd: root@pts/0,pts/1,pts/2 (sshd)
1872  0  Ss+    0:00.04 | | |-- -csh (csh)            \
2059  1  Is+    0:00.02 | | |-- -csh (csh)             | how?
2989  2  Is     0:00.02 | | `-- -csh (csh)            /
4668  2  S+     0:00.15 | |   `-- gstat -a
4372  -  Ss     0:00.04 | |-- sshd: root@pts/3 (sshd)
4374  3  Ss     0:00.15 | | `-- -csh (csh)
6731  3  R+     0:00.00 | |   `-- ps dax             <-- me
4519  -  Ss     0:00.05 | `-- sshd: root@pts/4 (sshd)
4521  4  Is     0:00.02 |   `-- -csh (csh)
5864  4  S+     0:00.04 |     `-- gstat -p           <-- also me
```
`pts/3` and `pts/4` is me. But how did someone else opened 3 simultaneous sessions via same `ssh` connection? Anyone happen to know how?


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## olli@ (Feb 14, 2019)

It's called session multiplexing. See the description of `ControlMaster` and `ControlPath` in the ssh_config(5) manual page, and the description of `MaxSessions` in the sshd_config(5) manual page, and the `-O` option (uppercase letter O, not the digit zero) of ssh(1).


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