Category Archives: Sysadmin

Likewise Open – problems rejoining domain after upgrade

Leave a reply

There seems to be a common problem with Likewise open not gracefully upgrading on Ubuntu, e.g. – upgrading a system from the distribution supplied Likewise-open 5 in Ubuntu 10.10 to the latest packages from the Likewise website (Likewise 6.0 at the time of writing).

The system in this case was an old Ubuntu 9.10 server using Likewise Open 5. After some patching and an update to the current vmware tools it started failing to authenticate domain users, so I decided to upgrade to the latest version. However after the upgrade I was getting an error when trying to join the domain:

Error: ERROR_FILE_NOT_FOUND code 0x00000002

The obvious solution is to remove all likewise packages and purge the config, however that didn’t seem to work either. What DID work, was removing & purging the config, manually removing a few directories that were not empty, purging a few other seemingly related packages which were marked as no longer required after the uninstall, and finally reinstalling.
Continue reading →

Bash script to alert when memory gets low

9 Replies

We have a web server that’s running out of memory about once every couple of weeks. The problem is that when it happens the swap file is totally full, the system is unresponsive and it usually needs a hard reboot. So it’s a bit difficult to debug. To avoid digging through log files I don’t understand I elected to put a script in /etc/cron.hourly which checks the total amount of free memory (including swap and physical). If there is less than 256mb free (this server has 512mb of ram and a 1gb swap so at this point the situation is serious), it dumps the process list to /tmp/processes.txt and sends me an email with it attached.

Note that mutt must be installed (‘apt-get install mutt’ on Debian/Ubuntu, or ‘yum install mutt’ on RedHat/CentOS). 

#!/bin/bash

free=`free -mt | grep Total | awk '{print $4}'`

if [ $free -lt 256 ]; then
        ps -eo %mem,pid,user,args >/tmp/processes.txt
        echo 'Warning, free memory is '$free'mb' | mutt -a /tmp/processes.txt -s "Server alert" [email protected]
fi

Then of course make it executable and symlink to cron.hourly:

chmod +x /etc/scripts/memalert.sh
ln -s -t /etc/cron.hourly/memalert.sh /etc/scripts/memalert.sh