Linux

Linux is for intelligent people.

Applying updates normally blocked

RHEL4:

$ sudo up2date --list
$ sudo up2date --update --force

RHEL5:

$ sudo yum check-update
$ sudo yum upgrade

Search for an application

$ yum search fooapp
$ yum list fooapp
$ rpm -qa | grep -i foo

Remove an rpm package

$ sudo yum remove package_name

Miscellaneous Linux Tech Notes

For keyword specific options (e.g. binding a MAC address to a specific eth port see: http://www.linux.ncsu.edu/moin/RealmLinuxServers/Configuring_Static_and_...
Whenever a machine's IP is moved on QIP type: ncsubless Make sure to enter the fqdn on the /etc/hosts & /etc/configsys/network files
To find out about what version of linux are we running and other CPU specs:
more /proc/version
more /proc/cpuinfo
more /proc/meminfo
cat /etc/redhat-release
To schedule shutdown of a redhat box: /sbin/shutdown -h hh:mm
uname reports the running kernel.
rpm -qa kernel\* will show you what's installed
netstat -antp (to see open connections)
To setup a service to automatically start at bootup: /sbin/chkconfig --level 2345 servicename on (where servicename must exist under /etc/init.d/)
For example /sbin/chkconfig --list sendmail (displays runlevels that sendmail is set to run on)
To check current RAID configuration: cat /proc/mdstat also used the /sbin/fdisk -l command to get more info. To learn more about RAID configuration check http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch26_:_L...

More Linux Commands

Useful Commands for Mac OS X and Linux

$ ls (insert any letters) TAB (hit TAB twice in Linux)
-will give you the files in the current directory that begin with (letters)

$ file file_name-this will return what kind of file the name file is

$ less file_name-less lets your scroll back up when viewing a file

$ ls -l | more
-the pipe command will string things together, in this case it uses the "more" command on the output of ls -l

$ man command_name
-gives description of command

$ info command_name
-more info than man command

$ apropos command_name
-gives all man pages for commands that might help with understanding command_name

$ touch -t 05070915 my_report.txt
-Used to change the date and time of a file. The first four digits stand for May 7 (0507) and the last four (0915) the time, 9:15 in the morning

$ find -name OR -mmin+0 -mmin -10
-the find command can be used to find files by name or age (this example does files in the last ten minutes)

$ grep
-grep is used to find words in files

$ who
-who is used to find out who is working on your system

$ whoami
-tells you which user you are

$ whatis
-explain the use of a command

$ whereis
-location of a command

$ date
-gives the date

$ last
-who logged into the machine recently

$ df
-how much disk space is used

$ du
-how large is a file

$ top
-see what processes are running on your machine (and percentage of CPU usage for each

$ ps
-see list of process running on the machine, descriptive

$ kill
-use kill in association with a PID to stop a process

$mount -t /dev/fd0 /floppy
-mounts a floppy
-t expresses the system type
-/dev/fd0 picks the hardware file to mount
-/floppy tells where to mount it

$ mount -t iso9660 /dev/hdb /cdrom
-mounts a CDROM
-iso9660 is a standard CD file structre

$ mount -t /dev/hda1 /mnt
-mounts another partition on the harddrive

$ umount /mounted_drive_name
-unmounts specified drive

$ tar -cvf tarfile_name.tar files_to_tar
-files to tar = *.txt, mary*.txt
-c is for create
-v verbose (show what files are)
-f make a file (f should always be last)
-z will compress the file as well; be sure to the name the file ".tar.gz" (see more info below on gzip)

$ tar -zxvpf
-this is used to unzip the file
-x used to extract the tar files
-p used to keep file permissions, dates, info, etc. about the tarred files

$ gzip your_tar_file.tar
-tar does NOT compress files, use gzip to compress your tar files

$ rm -fR /file_name
-this will remove a directory and everything below it

$ ln -s /source /destination
-create a sim link to files in other places

$ hdiutil makehybrid –iso -o outputfile.iso source
-create an iso file from source

$ bc
-built in simple calculator

$ sudo !!
-run sudo in front of the last command run

$ sh command.sh
-run a shell command in Mac OS X

$ open .ssh
-takes you to known_hosts file

$ chown -R username /filename
-changes the owner of /filename to /username

$ ifconfig eth0 inet 192.168.1.100
-sets ip address to 192.168.1.100

$ ifconfig eth0 netmask 255.255.255.0
-sets ip netmask

$ date “+%Y_%m_%d”
-displays date in format: yyyy_mm_dd

$ mkdir *

$( command here)
-you can run a command to be the argument of another command by starting another shell *

$ telnet IP/hostname port#
-you can check to see if a port is open on a machine using this

$ scp /path/file user@server.domain.com:/path/
-use this to run file transfer over ssh
-specify –r to copy an entire folder and all of it’s contents

CSC IT