"sudo su && somecommand" doesn't run somecommand

If you are trying to run the df command as root, you should instead do sudo df.

This is because with sudo su && df, you are basically executing sudo su first and then df.

Also make sure, your jenkins user can be sudo without password.

The sudo su launches a second shell, and the command containing the && df is waiting to be executed in the non-root shell, just after the sudo su shell exits successfully.

This could be what you're looking for:

sh -c 'sudo su - root -c "df"'

Edit: please note that I don't normally use or advocate the use of sudo su - root -c type of constructions. However, I have seen rare cases in which a program doesn't work properly when called via sudo/gksudo, but does work properly when called via su/gksu -- in such cases, a given user should try to use sudo -i first, and if that does not work, one might have to resort to sudo su - root -c or similar, as a workaround of sorts to deal with a "misbehaving" program. Since the OP used some similar syntax on his post, I assumed that his case could be such a workaround case, so I maintained the sudo su - root -c type of structure on my answer.