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 safety delete a file in Linux?
Answer:
Sometimes, you might have a very sensitive file that don't want others to recover, you might want to use the following command
shred -u password.txt
The command will overwrite the password.txt repeatedly, in order to make it harder for data recovery, and finally delete it.
How to change hostname in Ubuntu?
Answer:
To see the current hostname setting, see
# cat /etc/hostname
www.example.com
To change it, edit this file
sudo vi /etc/hostname
Save it and reboot your system and perform the step above to check again.
How to display swap information on Linux?
Answer:
With the following command
# cat /proc/swaps
Filename Type Size Used Priority
/dev/md4 partition 4192824 224 -1
It will display the current swap information.
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.
Permission denied when redirection with sudo
Answer:
When you are doing redirection with sudo, such as the following command
# sudo echo 1 > /proc/sys/vm/drop_caches
-bash: /proc/sys/vm/drop_caches: Permission denied
You will get permission denied as the redirection will be performed as the user calling sudo, not as the superuser. So if you don't have permission to write to the target file, you will get permission denied.
To solve the problem, use the following method
sudo sh -c 'echo 1 > /proc/sys/vm/drop_caches'
