bash - a complex scripting

Question

I would like to execute a series of commands upon reboot, inside a SCREEN environment. I can do this via my crontab:

@reboot /usr/bin/screen -d -m -S myPseudoDaemon /path/to/something.sh

...so I could just put the commands in 'something.sh'. What complicates this case, is that the series of commands includes a sudo and a chroot:

sudo -i # become root
chroot /opt/debianUnstable # enter the chroot-ed Debian unstable
/bin/bash # source my bash setting, including mandatory env vars
/path/to/whatever.sh # the actual "daemon"

Any idea how I could do this?

@devnull: That is already done - passwordless sudo works, but opens the root shell and waits there. I want to run the rest of the commands inside it... — angularJsNewbie
– angularJsNewbie, Commented Sep 20, 2013 at 8:31

jcb00s · Accepted Answer · 2013-09-20 09:07:51Z

1

When you execture chroot, you will have an interactive shell or run command with special root directory, which means your root have already been in the new root.

First you'd execute the shell in new root,

chroot [OPTION] NEWROOT /bin/bash --login

From the bash manpage, we know that when bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. So you'd probably add /path/to/whatever.sh to profile script which is relative to the new root.

answered Sep 20, 2013 at 9:07

jcb00s

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angularJsNewbie Over a year ago

Thanks, your suggestion is the closest to a solution. But if I did that, the user would no longer be able to login normally - he would always be executing the script... Is there a way to both have the --login effect (reading the config files) and running my script?

crafter · Accepted Answer · 2013-09-20 09:08:22Z

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Your /bin/bash is creating a shell. You should write :-

/bin/bash /path/to/whatever.sh # the actual "daemon"

answered Sep 20, 2013 at 9:08

crafter

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2 Comments

angularJsNewbie Over a year ago

If I do that, the env vars inside my .bashrc/.profile are not set. I run /bin/bash first to get to my 'default' profile.

crafter Over a year ago

Good point. you could 'source' the file. thegeekstuff.com/2010/07/execute-shell-script

xvdd · Accepted Answer · 2013-09-20 09:27:22Z

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Did you tried to schedule it in root crontab ?

It will allow you to chroot without password.

To run a command with your applicative user, you can use:

su -u <user> -c <command>

answered Sep 20, 2013 at 9:27

xvdd

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angularJsNewbie · Accepted Answer · 2013-09-24 10:21:43Z

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In the end, I solved this using the advise from jcb00s and Teg - but since I needed a specific part of my environment, I placed it in a script that executes in the chroot:

@reboot /usr/bin/screen -d -m -S autoLoginScreen /root/chrootPollAndBuildWithUnstable.sh

Inside /root/chrootPollAndBuildWithUnstable.sh:

# cat /root/chrootPollAndBuildWithUnstable.sh
chroot /opt/debianUnstable/ /pollAndBuildInsideChroot.sh

And inside the chroot-ed debian unstable filesystem, I do the final step...

# cat /opt/debianUnstable/pollAndBuildInsideChroot.sh 
su - <user> -c '/bin/bash /home/user/work/builder.sh'

...where the builder script sets the environment and proceeds with the build.

answered Sep 24, 2013 at 10:21

angularJsNewbie

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