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Altoid

Member

Registered: 2017-05-07

Posts: 1,592  

[SOLVED] crontab permission problem

Hello:

Now that my cron issues were taken care of, I now see the errors that crop up when it actually runs as intended.  8^7

My crontab has these three entries with the purpose of keeping log files to a manageable size till the time they get rotated:

# 1. For /home/groucho/.xsession-errors
# ---
0 */23 * * *  [ $(du -k .xsession-errors | awk '{ print $1 }') -gt 5000 ] && tail -200 /home/$(whoami)/.xsession-errors > /home/$(whoami$
# ---
#
# 2. For /var/log/boot (bootlogd)
# ---
0 */23 * * *  [ $(du -k /var/log/boot | awk '{ print $1 }') -gt 5000 ] && tail -200 /var/log/boot > /var/log/boot
# ---

# 3. For /var/log/cron.log
# ---
0 */23 * * *  [ $(du -k /var/log/cron.log | awk '{ print $1 }') -gt 5000 ] && tail -200 /var/log/cron.log > /var/log/cron.log
# ---

The first one has no issues, it is for the prolific .xsession-errors living at /home.

But the other two need admin rights:

groucho@devuan:~$ tail -200 /var/log/boot > /var/log/boot
bash: /var/log/boot: Permission denied
groucho@devuan:~$ 

groucho@devuan:~$ tail -200 /var/log/cron.log > /var/log/cron.log
bash: /var/log/cron.log: Permission denied
groucho@devuan:~$ 

My user belongs to a miriad of groups:

groucho@devuan:~$ groups
groucho adm lp mail dialout fax cdrom floppy tape sudo audio dip www-data backup video plugdev staff users crontab netdev lpadmin scanner saned fuse powerdev debian-exim
groucho@devuan:~$ 

As you can see, adm is one of them.
But doesn't adm have rights over /var/log/boot and /var/log/cron.log?

groucho@devuan:~$ 
groucho@devuan:~$ ls -l /var/log | grep adm |grep boot
-rw-r----- 1 root        adm    6639408 Apr  9 17:20 boot
groucho@devuan:~$ 

groucho@devuan:~$ 
groucho@devuan:~$ ls -l /var/log | grep adm |grep cron.log
-rw-r----- 1 root        adm     105594 Apr  9 18:35 cron.log
-rw-r----- 1 root        adm   14428210 Apr  4 06:50 cron.log.1
groucho@devuan:~$ 

What am I missing?

Thanks in advance,

A.

Head_on_a_Stick

Member

From: London

Registered: 2019-03-24

Posts: 3,125  

Website

Re: [SOLVED] crontab permission problem

-rw-r----- 1 root        adm    6639408 Apr  9 17:20 boot
[...]
-rw-r----- 1 root        adm     105594 Apr  9 18:35 cron.log
-rw-r----- 1 root        adm   14428210 Apr  4 06:50 cron.log.1

Those permissions indicate that root can read or write to the files but members of the adm group can only read them.

---

Brianna Ghey — Rest In Power

Altoid

Member

Registered: 2017-05-07

Posts: 1,592  

Re: [SOLVED] crontab permission problem

Hello:

... indicate that root can read or write to the files but members of the adm group can only read them.

I see.
Crontab runs as the user that added the scripts so my only options are:

1. to put the lines needing root credentials in /etc/cron.d.
2. add them to via sudo crontab-e to root's crontab.

Is this so?

Thanks in advance,

A.

Last edited by Altoid (2021-04-14 18:55:27)

Head_on_a_Stick

Member

From: London

Registered: 2019-03-24

Posts: 3,125  

Website

Re: [SOLVED] crontab permission problem

Yes, I think so.

But I would just use the size option described in logrotate(8) to control how big the files get before being rotated.

EDIT: and I would delete ~/.xsession-errors at the start of every X session because there doesn't seem much point keeping error logs from old sessions.

To wit:

echo 'rm ~/.xsession-errors' >> ~/.xsessionrc

See also https://wiki.debian.org/Xsession

Last edited by Head_on_a_Stick (2021-04-10 10:57:51)

---

Brianna Ghey — Rest In Power

Altoid

Member

Registered: 2017-05-07

Posts: 1,592  

Re: [SOLVED] crontab permission problem

Hello:

Yes ...

Right.
Further thinking about it, I see it makes sense.

But I would just use the size option described in logrotate(8) to control how big the files get before being rotated.

I recall (?) thinking about that but did not see the need for the rotated files.
I'll look into that, thanks for the heads up.

... would delete ~/.xsession-errors at the start of every X session ...
... doesn't seem much point keeping error logs from old sessions.

Yes, I have seen that done.
And taking into account how unintelligible they are ...

But I have found that they have been a sort of reference for comparison purposes between boots.
Not that I actually solved anything.  8^7

Thanks a lot for your input.

Best,

A.