Linux

If I install a new computer for myself (or if I do a fresh reinstall on an old machine), I want the computer have the software I am used to. To automatize this process, there a different approaches. If you use Ubuntu, you can use Ubuntu One to syncronize your software selection across many different machines (starting from Ubuntu 11.10 Oneiric Ocelot). If you use something else, it is getting tricky. You can use the following commands to generate a list of installed packages and load the list later for installation:
dpkg --get-selections > installed-packages.lst


My mysqld runs on Ubuntu Hardy and after replacing the complete mysql data with a dump from another server the "/etc/init.d/mysql stop" command fails, because the system administration account doesn't work anymore. So I had to recreate it again:
GRANT ALL PRIVILEGES ON *.* TO 'debian-sys-maint'@'localhost' IDENTIFIED BY 'password' WITH GRANT OPTION;
The password can be obtained from /etc/mysql/debian.cnf.

Finding files with the find command is actually more difficult than it should be.
This finds and lists the largest files (more than 200 MB) on the whole file system:
find / -type f -size +200000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
The same, but simpler syntax:
find / -size +200M -ls
This finds the most recently changed files under the current directory:
find . -type f -printf '%TY-%Tm-%Td %TT %p\n' | sort