Recover "ps" command

Solution 1:

Using dpkg -S /bin/ps will tell you that this program is in the procps package. Reinstall it using apt-get install --reinstall procps.

Solution 2:

Using the Packages website

The http://packages.ubuntu.com/ site comes in handy in such situations.

Example: search package contents for ps reveals the procps package.

Using the command-not-found feature

Type the command misspelled and search the suggested packages:

$ ps-
No command 'ps-' found, did you mean:
 Command 'psi' from package 'psi' (universe)
 Command 'psc' from package 'sc' (universe)
 Command 'psf' from package 'tcm' (universe)
 Command 'ps' from package 'procps' (main)