Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
How to check which directory used up most of the disk space?
Answer:
For example, assume you are at /usr/local, you want to generate a report on disk space usage on all the sub directories, you can use the following command
# du -k * | sort -n
.
.
14564 share/man/man3
14816 share/man
16624 share/perl/5.10.0
16628 share/perl
33060 share
It will give you a very clear and useful report.
How to ping a web site periodically
Answer:
1. Setup a cron job
crontab -e
2. Enter the job detail as following
1 * * * * /usr/bin/wget -O - -q -t 1 http://www.example.com/cron.php
3. Fine tune the crontab configurations if needed.
How to alter the priority of running processes
Answer:
The basic syntax is as the following
renice {priority} pid
Where priority range from -20 to 19 (lowest priority)
For example, to set the priority of pid 755 to -19, try
sudo renice 19 755
If you want to set by process name instead of pid, you can use
sudo renice 19 `pgrep apache2`
Where apache2 is the process name you want to set.
How to return the directory portion of a pathname
Answer:
Use the "dirname" command, e.g.
# dirname /usr/sbin/ufw
/usr/sbin
How to add line number to a file?
Answer:
The easiest way is to use the "sed" command
sed = test.txt | sed 'N; s/^/ /; s/ *\(.\{6,\}\)\n/\1 /'
