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I want to start screen and put a couple of programs running inside on startup. I've seen many similar posts but none answered my question. so I put in rc.local following 2 lines:

  screen -dmS scr bash -c 'ytop; exec bash'
  screen -S scr -X screen 1 bash -c 'nvtop; exec bash'

which works fine, but when I enter this screen, once logged in to the server, and want to create new screen, it doesn't have environment variables in it. How can I start it in the way that would have all root's envars?
new window looks like this:

sh-5.1#

$PATH in window is
/usr/bin:/bin

Yet in the rc.local created windows $PATH (/usr/bin:/bin) is the same, but the prompt is normal, so it looks that it reads /etc/profile
Window initialized by rc.local has normal prompt:

[root@mysrv ~]#

PATH is also a bit more than fresh window, but not same as if I start screen manually from the terminal as root

echo $PATH
usr/lib64/qt-3.3/bin:/usr/bin:/bin


When I start screen by myself it's normal prompt.

[root@mysrv ~]#

and

echo $PATH
/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin

Interestingly if I exit ytop it shows me proper prompt. Only when creating new screen somehow looses this envars.
I tried also running:

su - root -c `screen -dmS scr bash -c 'ytop; exec bash'`

but I get the same result.
Regards

DenisZ
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2 Answers2

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I think your problem here is the session-handling of bash. Bash - like any other shell interpreter - detects if it is started in the backgroud, or if it is attached to a terminal ( Interactive / Non-interactive mode ). Background is found here. My guess is, that your problems are solved by providing the -l switch to the first bash command:

screen -dmS scr bash --login -c 'ytop; exec bash'

The --login switch makes bash read all startup files, like /etc/profile, ~/.bash_profile, ~/.bash_login, and ~/.profile - which should contain the environmental variables you are missing.

Martin
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  • Thanks @Martin, but it didn't work when ran from `rc.local`. Maybe I would need to specify user, but didn't find it manual how to. But interesting really is i I quit `ytop` in screen one it shows me normal bash prompt (so obviously it read `/etc/profile`, `~/ .bash_profile` files. When I enter and attache screen and create new screen then it suddenly looses all those variables. – DenisZ May 31 '21 at 13:51
  • Hmm... okay, that is weird. The --login option doesn't have user credentials; it changes only the way bash is run. (use ```su - ``` to start a process as a different user). If the problem is only with the second screen command, why don't you create a second session like this: ```screen -dmS scr2 bash -c 'nvtop; exec bash'``` – Martin May 31 '21 at 14:02
  • I tried putting into `rc.local` su - root -c `screen -dmS scr bash -c 'ytop; exec bash'`, but same result, maybe are the quotes. What I do normally is always have several screens within one screen session open on each server, so I'd like to create a few starting screens automatically every time server is rebooted. Then I login go to screen and add new screens. I want them all under one session, so it's easier to manage. – DenisZ May 31 '21 at 16:57
  • the ```rc.local``` is executed as root, so ```su - root``` does not change anything. – Martin May 31 '21 at 17:14
  • I checked `$PATH` and it is `/usr/bin:/bin`, whereas if I start screen manually is `/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin`, so also any programs that I start without this path would start. still interesting is windows that I start within rc.local have good PS (prompt) but as mentioned starting new one doesn't carry over `$PS` variable from `/etc/profile` – DenisZ Jun 01 '21 at 16:19
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I finally found a solution. It's very simple. I had to edit file /etc/screenrc and add following line

defshell -/bin/bash

And than it works normally when starting screen in detached mode (screen -dmS scr bash -c 'ytop; exec bash'), and also when later entering this screen and creating new window, bash environment will be present.

bellow solution also didn't work.

So to start screen with normal shell and variables you have to do it >with init, so :

su - root -c screen -dmS scr bash -c 'ytop; exec init'

So this will have normal environment like if you manually start screen >and detach it.

DenisZ
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