Any file executed once when system starts up

Question

Is there any config file that is evaluated once, everytime operating system starts up. bashrc does not qualifies since it gets evaluated everytime a gnome terminal starts..

Answer 1

There are 2 places I use when I need to add "run-once" commands:

Once at every user login (be it Graphical/GDM or text/console login): ~/.profile

Pros:

• It works even if no GDM/X11/Graphical server is used. Meaning it will work with SSH and text-mode logins
• It is NOT evaluated when a gnome terminal starts, as required. ONLY at login
• Executed with user priveleges, its secure while allowing full access to personal scripts.
• Run after all mounts are done, so the whole filesystem is avaliable.

Cons:

• If a user logs in, logs out and logs in again, it will be executed again, once per login. So its not a "true" system start up only. But it may suit your need.
• Since this is executed even in text-mode logins, its advisable NOT to place any command that requires a GDM/X11 server (like synergy daemon)
• Bash is only used with text-mode logins. So if using GDM, no bashisms are accepted in the script, since Ubuntu will run it with dash

Once when GDM starts (before any user logs in): /etc/gdm/Init/Default

Pros:

• Executed only once, no matter how many users log in or out
• Can be used for both text and graphical commands
• Run after all mounts are done, so the whole filesystem is avaliable.

Cons:

• Run using gdm user. So personal scripts and path to them must be world-readable and executable
• Cannot be used if no GDM server is used (duh). So it wont run in text-mode start-ups
• Again, not run in bash, so bashisms must be avoided.

Use the method that suits your need.

Answer 2

cron can be of help here.

Besides starting something on a minute,hour,day of week, month etc it also has some special operations:

@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".

Editing is done from command line with the following command:

sudo crontab -e

at the bottom of the file (below the # m h dom mon dow command) you can add a line that executes what you want like so @reboot /directory/to/file will execute /directory/to/file during boot.

Just one warning: you need to make sure that there is no output from that script or that the output is redirected to a file (or /dev/null) since there is no display for cron to send the output (and it will end the operation).

Example sudo crontab -e

# For more information see the manual pages of crontab(5) and cron(8)
# 
PATH=/usr/sbin:/usr/bin:/sbin:/bin
# m h  dom mon dow   command
@reboot /usr/bin/testscript

and...

cd /usr/bin/
sudo vi testscript 
echo "works" >/tmp/testing
chmod 775 testscript

Now for a reboot... And here is a working example:

ls -l /tmp/testing
-rw-r--r-- 1 root root 6 2011-05-29 08:34 /tmp/testing
rinzwind@discworld:/tmp$ more /tmp/testing
works

Answer 3

Have you looked into cron jobs? You can set one at reboot @reboot in your crontab

Answer 4

Beside other answers, you can put your startup (superuser) commands in /etc/rc.local.