Question

8

Backing up for syslog/dmesg/message to different folder

rated 0 times [ 8] [ 0] / answers: 1 / hits: 2244 / 1 Year ago, sun, february 5, 2023, 7:31:25

I have an assignment where I am required to back up the /var/log/dmesg, /var/log/syslog and /var/log/message to text files in a different folder such as the Desktop. It will also create a file called Execution.txt to record the date and time whenever the bash script is run. I do have this code that I've written yet every time I run it, it gives me:

./bash.sh: line 7: /var/log/dmesg: Permission denied

./bash.sh: line 8: /var/log/syslog: Permission denied

./bash.sh: line 9: /var/log/message: Permission denied

However, it does create these files on the desktop, but the message and dmesg files are empty. I was wondering if this is normal or have I done something wrong? Below is the code that I have written so far. Any help would be appreciated. Thanks!

#!/bin/bash



cat /var/log/dmesg l nl >> /home/administrator/Desktop/dmesg

cat /var/log/syslog l nl >> /home/administrator/Desktop/syslog

cat /var/log/message l nl >> /home/administrator/Desktop/message



echo ' ' > /var/log/dmesg

echo ' ' > /var/log/syslog

echo ' ' > /var/log/message



date >> /home/administrator/Desktop/execution.txt

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tusmuumu

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1 Year ago

answered 1 Year ago ticeate · Accepted Answer

I suspect you just don't have access to them from the user that is running this script. Look at the file ownerships:

$ ls -l /var/log/{dmesg,syslog,message}

ls: cannot access /var/log/message: No such file or directory

-rw-r----- 1 root   adm 86384 Mar  9 11:12 /var/log/dmesg

-rw-r----- 1 syslog adm 18553 Mar 25 13:25 /var/log/syslog

You could read from these files if you had a user in the adm group but you'd not be able to write. The first user on a system is typically a member of the adm group but if your ~/Desktop copies are empty, I'd suggest your user isn't (check with the groups command). You do have a few options.

You could either look at adding ACL permissions for your user. These are separate from the standard permissions and adding explicit read/write access to your user doesn't really affect anything else. Which is nice.
```
sudo apt-get install acl

sudo setfacl -m u:$USER:rw /var/log/{dmesg,syslog,message}
```
This might need a reboot to take. You might even need to change your fstab. I haven't but ACLs seem to work okay here so I'm assuming that's not required any more.

You could change the unix permissions on the file. The safest way of doing this would be to add your user to the adm group and then to enable group write on those files:
```
sudo usermod -a -G adm $USER

sudo chmod g+w /var/log/{dmesg,syslog,message}
```
You'll need to log out and in again to see the effect.

Or you could let anybody read and write these files. This could be a security risk so I'm not giving you code... But honestly, while possible, you probably don't want this.

The other option is simply running the script as root with sudo ./scriptname. The downside of this is that anything this script does will be done as root. That includes creating new files (which >> can if the file doesn't exist already) and that can be a pain for the user.

And if this isn't academic curiosity and you're actually trying to get some work done in the best possible way, there are tools that do these things for you but better. You really want to look at logrotate. This Digital Ocean tutorial is the cleanest one I can find quickly.