Linux/Unix:Generic
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- Force a reboot (e.g. when mount commands are hanging)
echo 1 > /proc/sys/kernel/sysrq
echo b > /proc/sysrq-trigger
- ulimit -Sv 12000000
- Set max memory to use to 12GB for this process (with option to increase (-S))
- cp -rL
- Copy recursively and dereference symbolic links (copy the file, not the link)
- top
- List process resource usage. By default having the most CPU-intensive process on top. Press > to have it sort on another column. Press 1 to have usage for each CPU apart.
- lscpu
- List CPU information
- free
- Show memory usage
- cat /etc/sysctl.conf|grep swappiness
- Check swappines (the eager the system will swap with). A higher number means more swapping will happen. 0 is not no swapping but minimal swapping.
- uname -a
- Show kernel version
- mountpoint -q <directory>
- Check if <directory> is in use as mountpoint
- chage -l <username>
- Show password aging status
- PS1="[\u@\h \W]\$ "
- Set shell prompt to '[username@hostname <curdir>]$ '
- \w for whole current path
RedHat (RHEL)
- /etc/redhat-release
- Redhat version installed
- for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done
- Find swapspace usage per process
- yum list
- Show all packages on the rpm-server
- yum install <packagename>
- Install a package from a rmp-server
Bash
- :
- No operation (NOP)
Raspberry pi autologon
In /etc/lightdm/lightdm.conf comment this line out (by putting a # in front of it)
lightdm.conf:autologin-user=pi