1- Save man-page as pdf
man -t awk | ps2pdf - awk.pdf
2- Duplicate installed packages from one machine to the other (RPM-based systems)
ssh root@remote.host "rpm -qa" | xargs yum -y install
3- Stamp a text line on top of the pdf pages to quickly add some remark, comment, stamp text, ⊠on top of (each of) the pages of the input pdf file
echo "This text gets stamped on the top of the pdf pages." | enscript -B -f Courier-Bold16 -o- | ps2pdf - | pdftk input.pdf stamp - output output.pdf
4- Display the number of connections to a MySQL Database
Count the number of active connections to a MySQL database.
The MySQL command âshow processlistâ gives a list of all the active clients.
However, by using the processlist table, in the information_schema database, we can sort and count the results within MySQL.
mysql -u root -p -BNe "select host,count(host) from processlist group by host;" information_schema
5- Create a local compressed tarball from remote host directory
ssh user@host "tar -zcf - /path/to/dir" > dir.tar.gz
This improves on #9892 by compressing the directory on the remote machine so that the amount of data transferred over the network is much smaller. The command uses ssh(1) to get to a remote host, uses tar(1) to archive and compress a remote directory, prints the result to STDOUT, which is written to a local file. In other words, we are archiving and compressing a remote directory to our local box.
6- tail a log over ssh
This is also handy for taking a look at resource usage of a remote box.
ssh -t remotebox "tail -f /var/log/remote.log"
7- Print diagram of user/groups
Parses /etc/group to âdotâ format and pases it to âdisplayâ (imagemagick) to show a usefull diagram of users and groups (donât show empty groups).
awk 'BEGIN{FS=":"; print "digraph{"}{split($4, a, ","); for (i in a) printf "\"%s\" [shape=box]\n\"%s\" -> \"%s\"\n", $1, a[i], $1}END{print "}"}' /etc/group|display
8- Draw kernel module dependancy graph.
Parse `lsmodâ output and pass to `dotâ drawing utility then finally pass it to an image viewer
lsmod | perl -e 'print "digraph \"lsmod\" {";<>;while(<>){@_=split/\s+/; print "\"$_[0]\" -> \"$_\"\n" for split/,/,$_[3]}print "}"' | dot -Tpng | display -
9- Create strong, but easy to remember password
Why remember? Generate!
Up to 48 chars, works on any unix-like system
read -s pass; echo $pass | md5sum | base64 | cut -c -16
10- Find all files larger than 500M and less than 1GB
find / -type f -size +500M -size -1G
11- Find size of directories and files in current directory
du -h -d 1
12- Limit the cpu usage of a process
This will limit the average amount of CPU it consumes.
sudo cpulimit -p pid -l 50
13- Show the difference between two dirs
diff -qr /var/some/dir1 var/some/dir2
