How to let eshell remember sudo password for two minutes?

Question

In a general term runing bash, when I run a sudo ... command, bash will remember my password for a while. This makes package management task easier.

For example:

sudo apt-get update
# password ......
sudo apt-get install turing-brain
# execute without requiring password again.

Is it possible to accomplish it in eshall?

(I know term or ansi-term in Emacs can do this. But eshell integrate better with Emacs.)

Answer 1

First of all check which sudo is executed in your eshell session. It can be your system’s sudo:

$ which sudo
/path/to/system/wide/sudo
$ which *sudo
/path/to/system/wide/sudo

or eshell’s sudo:

$ which sudo
sudo is a compiled Lisp function in `em-tramp.el'
$ which eshell/sudo
eshell/sudo is a compiled Lisp function in `em-tramp.el'

Eshell’s sudo uses TRAMP's su or sudo method. These commands are in the eshell-tramp module, which is disabled by default.

I will cover eshell’s sudo case, because it is internal to Emacs and it does not depend on your OS distro:

1. Load eshell-tramp module:

   (require 'em-tramp) ; to load eshell’s sudo
   

2. Switch to eshell’s sudo

   • by prefering built-in commands

     (setq eshell-prefer-lisp-functions t)
     

     It seems that in Emacs 24.4 we need to set

     (setq eshell-prefer-lisp-variables t)
     

   • by creating an alias (execute snippet in eshell)

     alias sudo 'eshell/sudo $*'
     

     Aliases defined (or deleted) by the alias command are automatically written to the file named by eshell-aliases-file, which you can also edit directly (although you will have to manually reload it).

3. Finally enable password caching for eshell’s sudo (and TRAMP):

   (setq password-cache t) ; enable password caching
   (setq password-cache-expiry 3600) ; for one hour (time in secs)
   

PS If you have changed your prompt with eshell-prompt-function, then remember to adjust prompt regex eshell-prompt-regexp accordingly. Wrong prompt regex can break some eshell functionality — including password detection.

Answer 2

To get sudo working in Emacs 26 (probably the same for Emacs 25) without making an alias I had to add eshell-tramp to eshell-modules-list.

(add-to-list 'eshell-modules-list 'eshell-tramp)