[GTALUG] How much do you know about how linux executes binaries?

[Nicholas Krause]

On 12/11/19 12:27 PM, Lennart Sorensen via talk wrote:
> Someone at work just made a slight mistake:
>
> root at ECA:~# cd /var
> root at ECA:/var# mv core.* /*   [clearly that trailing * was not meant to be there]
> [bunch of errors about target already existing]
> root at ECA:/var# ls
> -bash: /bin/ls: No such file or directory
> root at ECA:/var#
>
> So what do you do now?
My first idea would be to echo $PATH and see if the path is messed up or
/etc/profile or other bash startup scripts are not screwed up. Not sure what
the errors were but that's the first place to start.

If that's fine then /bin is a symlink from /usr/bin these days to something
in /usr/bin and I would less if my symlinks for /bin are now screwed up
and fix that. The real question through is how much of root is overwritten
in this case.



Nick
>
> I was able to fix it in about 5 minutes without using anything other
> than what was on the running system?  Interesting little problem.
>
> The original state of the system was:
>
> root at ECA:/var# ls -l /
> drwxr-xr-x    2 root     root          4096 Dec  9 11:47 bin
> drwxr-xr-x    2 root     root          4096 Dec  6 11:16 boot
> drwxr-xr-x   10 root     root          2340 Dec  6 11:18 dev
> drwxr-xr-x   46 root     root          4096 Dec  9 11:48 etc
> drwxr-xr-x    6 root     root          4096 Dec  5 12:09 home
> lrwxrwxrwx    1 root     root            10 Dec  5 12:09 init -> /sbin/init
> drwxr-xr-x    4 root     root          4096 Dec  5 12:09 lib
> drwxr-xr-x    5 root     root          4096 Dec  5 12:09 lib64
> drwx------    2 root     root          4096 Dec  5 12:09 lost+found
> drwxr-xr-x    2 root     root          4096 Nov 19 10:07 media
> drwxr-xr-x    4 root     root          4096 Dec  5 12:09 mnt
> drwxrwxrwx    6 root     root          4096 Dec  5 12:24 opt
> drwxr-xr-x    3 root     root          4096 Dec  5 12:09 persistdata
> drwxr-xr-x    5 root     root          4096 May 25  2018 persistent
> dr-xr-xr-x  473 root     root             0 Dec  6 11:17 proc
> drwxr-xr-x    5 root     root          4096 Dec  9 11:38 root
> drwxr-xr-x   12 root     root           780 Dec  6 11:18 run
> drwxr-xr-x    2 root     root          4096 Dec  9 11:47 sbin
> dr-xr-xr-x   11 root     root             0 Dec  6 11:17 sys
> drwxrwxrwt    8 root     root           400 Dec 11 12:14 tmp
> drwxr-xr-x   12 root     root          4096 Dec  5 12:09 usr
> drwxr-xr-x   15 root     root          4096 Dec  5 12:15 var
>