Few basic unix command to remember

#command to find linux model and versios
uname -m = i686
uname -r = 2.6.9-42.0.3.ELsmp or2.6.18-8.el5(centos)or2.6.16-xenU(fc-xen)
uname -s = Linux
uname -v = #1 SMP Fri Oct 6 06:21:39 CDT 2006
uname -a =Linux imagic.planet.com 2.6.18-8.el5 #1 SMP Thu Mar 15 19:57:35 EDT 2007 i686 i686 i386 GNU/Linux

#cat /etc/distro for linux
#cat /etc/issue for ubuntu

#add a user to home directory
useradd -d /home user
#give permission to a file
chmod 755 filename(755-wrx rx rx)

#user with nologon permission
vi /etc/passwd
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin

#ownership to file
chown root:root file(user:group)

#delete a user
userdel user

#adding a user to group
usermod -g group user

#check user present in that group
groups user

#delete a user from group
usermod -a -G group user

#add a user to wheel group
vi /etc/group

#permission wheel user to system
## Allows people in group wheel to run all commands
%wheel ALL=(ALL) ALL

## Same thing without a password

##permission to user to few services

user ALL=/etc/init.d/httpd /sbin/httpd

#setuid user
chmod u+s file
it willbe like -rwsr-xr-x user group file

#setuid user
chmod g+s file

#command to check uid for user
uid=502(user) gid=10(wheel) groups=10(wheel)

id root
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel)

#process to background

#check with jobs -l

#put it front
fg %id

#command to run the process when shell is closed
nohup process

#command to check memery usage of procees
top or htop

#command to kill process
kill -9 pid or process

#part of the name
pkill -9 httpd

#kill all
killall -l httpd

# Kill TERM processes owned by www
pkill -TERM -u www
# Kill every process accessing /home (to umount)
fuser -k -TERM -m /home

#switch to other user
su -l user

#run a program using a sudo user(edit /etcsudoers and add user
user ALL=/etc/init.d/httpd or allow wheel and add user to wheel group)
sudo /etc/init.d/httpd start
sudo restart

#enable/disable firewall

#delete a oneday previous file in a dir

find /tmp -mtime +1 -type f -exec rm -f {} \;

# find all files last modififed yesterday
find . -mtime 1 -type f -print

#Delete log and use crontab
20 8 * * * echo “” > /usr/local/apache2/logs/access_log

# List the crontab
crontab -l crontab -e (edit)

#check if cron run
egrep -ir “access_log” /var/log/cron (check if run)

#check last accessed time from log
head -n10 /usr/local/apache2/logs/access_log


Posted on October 25, 2013, in LInux Based. Bookmark the permalink. Leave a comment.

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