LFCS Commands
Commands needed for Linux Foundation Certified Sysadmin.
Processes
ulimit
- man page
- get/set the resource limits of processes
- restrict: processes cant exhaust the system's resource
- expand: set enough resource to run a propgram properly
- hard limit: the possible maximum of resource, set by root
- soft limit: the possible maximum of resource for user, cant exceed hard limit
- users and
root
has different limits - the settings are valid for the current shell, to modify persistent, write to
/etc/security/limits.conf
- get all limit:
ulimit -a
- set the limit of open files:
ulimit -n 2048
ps
- man page
- show current processes
- list all processes:
ps -elf
orps -aux
nice
- man page
- set the starting process priority level
- higher nice level means lower priority
- range: -20 to 19
- run a script with lower priority:
nice -n 10 ./script
ornice -10 ./script
- run a script with higher priority:
nice -n -10 ./script
ornice --10 ./script
renice
- man page
- set an already runnning process priority level
- increase a PID's priority level:
renice -n 10 2000
orrenice +10 2000
- lower a PID's priorty level:
renice -n -10 2000
orrenice -10 2000
ldd
- man page
- list the shared libraries needed to a binary
- list the shared libraries need by
ls
:ldd /bin/ls
ldconfig
- man page
- generally runs at boot time
- used to build a cached database of shared libraries
ipcs
- man page
- get informations about IPC facilities
- to list facilites with PID:
ipcs -p
Signals
kill
- man page
- send a signal to a process
- list signals:
kill -l
- SIGTERM is the default signal, if the number ommited
- only accept PID!
- kill process using number:
kill -n 9 2000
orkill -9 2000
- kill process using name:
kill -s SIGKILL 2000
orkill -SIGKILL 2000
killall
- man page
- kill all processes (those that the caller user can kill) with the given name
- the default signal is SIGTERM
- kill every firefox instance with number:
killall -9 firefox
- kill every firefox instance with name:
killall -SIGKILL firefox
pkill
- man page
- send signal to a process with a criteria
- kill very firefox instance of user
g0rbe
:pkill -u g0rbe firefox