Linux

In Linux, you can simplify some of your SSH commands using an SSH config file. For example, create a file named config in your ~/.ssh directory with something like the following:


Host bar
HostName bar.examplecom
User bar user

Host foo
HostName foo.example.com
User foouser

This will allow you to ssh into the specified hosts using short commands such as ssh foo and ssh bar.

I ran into this issue a couple of days ago and cannot recall the exact error message. However, the problem was effectively that aptitude could not install the new kernel update because my partition had apparently run out of space. An interrupted update to Klipper is one thing and the Linux kernel a whole 'nother kettle of fishies. Thinking that I simply needed to free up some space on my partition, I checked the current status via df. I surprisingly had 30% of free space still left lying about (my /home is mounted on a different partition). So what ...

Since I keep forgetting this shortcut, here it is for posterity. Activating GNU Screen's scrollback feature can be done by pressing CTRL + a + [. This is especially handy when you are using Screen from within PuTTY.

While a number of sites provide additional Vim-esque shortcuts to navigate within the buffer, I've been able to get by fine with just the navigational arrow keys on my keyboard.

This is my week of playing around with mail servers and I have been keeping an eye on the logs on a regular basis. I noticed that the auth.log was riddled with millions of these pointless (from my POV anyhow) log entries:
CRON: pam_unix(cron:session): session opened for user root by (uid=0)
CRON: pam_unix(cron:session): session closed for user root


While trying to debug a postfix authentication issue in Debian 6, I had to use testsaslauthd to test things out:
testsaslauthd -s smtp -u foo@example.com -p test

only to get the following error:
connect() : No such file or directory 0

This is apparently because a lot of people (and authors) follow the same guide for configuring postfix and saslauthd. One of the steps missing is to symlink and saslauthd directory to a location within postfix. To fix:

If you've ever worked with Debian or Ubuntu servers, you've very likely had to set up a firewall at some point or the other. However, any changes that are made are not saved and loaded if the server is ever rebooted. The following is a quick guide on how to get this happening:

(root or sudo access is required)

My upgrade from Lucid to Precise did not go well and I've been battling errors ever since. I ran into the following error when trying to reinstall the php5-gd extension for PHP:
No apport report written because MaxReports is reached already

After my upgrade from Lucid to Precise (and thereby, from MySQL 5.1 to 5.5), I found that my MySQL instance was not running. When I tried to start the service all I got back was that it had failed to start.

I checked the system log (sudo tail /var/log/syslog) to see if I could divine the cause of this issue and I found the following messages:
init: mysql post-start process (5075) terminated with status 1
mysql respawning too fast, stopped

After an upgrade from Lucid to Precise, my PHP install started complaining about a library:

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20090626+lfs/gd.so'

While I've got a hunch that the actual problem is related to issues I had during the upgrade, turning this error (and other similar ones) off is as simple as going into /etc/php5/conf.d and renaming the file, in this case gd.ini to something like gd.ini.bak.

I needed to upload the contents of a lengthy log file to a site earlier today. There was no option to simply attach the file. I was instead asked to just paste its contents. I suppose that I could have opened the file in an editor like Kate and copied its contents to the clipboard. But I became curious as to the possibility of accomplishing this from within the terminal. A little googling revealed the existence of a utility named xsel for this very purpose.