Problem
You would like to know the release of your CentOS server but the cat /etc/issue does not work.
Solution
Try with the following:
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cat /etc/centos-release |
or with:
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cat /etc/redhat-release |
Problem
You have a bash script that accepts parameter(s) but you want to give a default value for a missing parameter.
Solution
For example you have a script that accepts a parameter with the year and month (ie 201703), but you want to give it a default of two months ago if the parameter is missing.
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#!/bin/bash LM=$(date -d '2 month ago' +%Y%m) YEARMONTH=${1:-${LM}} echo $YEARMONTH |
Problem
You would like to know what are the biggest nn files in your linux computer.
Solution
Run the following to give you the 20 largest files:
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sudo du -ahx / | sort -rh | head -20 |
taken from Linux Journal Issue 275 March 2017
Problem
You would like to find out the serial number of your Lenovo laptop, but without switching it off and taking the battery off.
Solution
You can run the following to get your laptop’s details including the serial number:
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sudo dmidecode -t system |
Taken from the post here
Problem
Looking at your /var/log/syslog you see entries every few seconds like the following:
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Mar 1 15:44:52 L530 systemd-udevd[11464]: failed to execute '/lib/udev/socket:@/org/freedesktop/hal/udev_event' 'socket:@/org/freedesktop/hal/udev_event': No such file or directory Mar 1 15:44:52 L530 systemd-udevd[11451]: Process 'socket:@/org/freedesktop/hal/udev_event' failed with exit code 2. Mar 1 15:44:54 L530 systemd-udevd[11479]: failed to execute '/lib/udev/socket:@/org/freedesktop/hal/udev_event' 'socket:@/org/freedesktop/hal/udev_event': No such file or directory Mar 1 15:44:54 L530 systemd-udevd[11466]: Process 'socket:@/org/freedesktop/hal/udev_event' failed with exit code 2. |
Solution
Seems that hal is not used in newer Ubuntu versions, so you can remove it:
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sudo apt-get purge hal |
Taken from the answer here
Problem
You want to remove a certain line from your server’s bash history, if for example you pasted a password in the wrong place.
Solution
Use the two steps:
1. history -d
2. history -w to write in-memory history to the history file ~/.bash_history
as described here
Problem
You would like to change the default editor for crontab from nano to vim.
Solution
Add the following to the ~/.selected_editor:
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SELECTED_EDITOR="/usr/bin/vim" |
or run the select-editor and choose vim-basic (4)
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server# select-editor Select an editor. To change later, run 'select-editor'. 1. /bin/ed 2. /bin/nano <---- easiest 3. /usr/bin/mcedit 4. /usr/bin/vim.basic 5. /usr/bin/vim.tiny Choose 1-5 [2]: 4 |
Problem
You would like to quickly convert a number from a different base system (i.e. binary, octal, hexadecimal), to decimal.
Solution
Use the echo $(()) shell command to convert it passing it the current base system and the number, as in $((2#101010)) or using the O for octal or 0x for hexadecimal notations.
Examples:
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echo $(( 16#FF )) 255 echo $(( 0xFF )) 255 echo $(( 8#21 )) 17 echo $(( 021 )) 17 |
Taken from Linux Journal’s Work the Shell column (March 2016)
Problem
You have received multiple zip files that were originally one big zip file, possibly from windows, and you want to put them back together and unzip them in linux.
Solution
So if your file names are for example called: file1.zip file2.zip etc, you can do the following:
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cat file* > one_file.zip unzip one_file.zip |
Problem
You are given a patch file to apply to your git repository but using git apply does not work. No errors reported but no changes applied neither.
Solution
Try to use the patch command command possibly with the -p1 parameter like:
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patch -p1 < path_to_the_patch_file.patch |
NOTE: Make sure that you are in the right folder relative to the file path in the patch file