Linux command guide

Getting Help

man <command> – Display command help

man find | grep <search string> – Locate specific help text within the manual

info – Provide man help in a different format

Directory navigation, basic shell tasks, and File Management

cd – Change working directory

cd .. – Change to parent directory

cd ~ – Change to home working directory

pwd – Display working directory

echo <line of text> – Display the line of text (useful for user friendly scripting)

echo $PATH – Display assignment to the environmental variable

time <command> - Time how long <command> took to execute

ls – Lists files in the current working directory

ls -a – Shows hidden files (hidden files start with a dot) as part of file listing

ls -l – Shows file detail

ls –F – Shows File type as part of file listing

history – Records commands typed at command prompt

    Ctrl+R to begin a backward search through history
    Ctrl+S to search forward through history
    Up Arrow and Down Arrow to move a line at a time through history

mkdir ch1 – Creates new directory ch1

mv file1 file2 – Moves file file1 to file2, renames file1 to file2

mv testfile changedfile

less – View file contents page-by-page

unset MYNAME – Removes the environment variable assignment assigned to MYNAME

exit – Terminate shell

cp -R one newone – Copies directory /one recursively to a new directory named /newone

rm etcbackup.tar.gz – Deletes file

Redirection and piping

ls > List-of-files.txt – Write list of files in current working directory to the file, List-of-files.txt

pwd >> List-of-files.txt – Append current working directory to the file “List-of-files.txt”

ps ax | grep string – Pipe output of ps ax to grep which searches for string.

Text processing commands

cat – Concatenate files together

cat /proc/interrupts – Display information from interrupts file (querying kernel about interrupts)

join – Merge file data from multiple files

sort – Sort file contents

nl – Generate line numbers for each line in a file

tail -20 /var/log/syslog – View last 20 entries posted to syslog file

less – File paging utility

grep string /var/log/* – Search for all occurrences of string in all log files in /var/log directory

Package Management

rpm Utility

    rpm -q zsh – Check if RPM package zsh (z shell) is installed
    rpm -i zsh-4.3.9-4.fc11.i586.rpm – Installs the zsh RPM package
    remove zsh: rpm -e zsh – Uninstalls the zsh RPM package

yum Utility

    yum install zsh – Downloads and installs zsh package

apt-get Utility

    sudo apt-get install alien – Downloads and installs the program “alien”
    sudo apt-get install chkconfig – Downloads and installs the program “chkconfig”
    sudo apt-get remove package – Remove package
    sudo apt-get install sysv-rc-conf - Provides gui view of all services running at each runlevel (works under server)
    apt-get autoremove – Removes additional programs associated with the main package installation

ldd /bin/ls – Display information about libraries used by the ls program

Useful Management Commands

ps aux –

top –

kill pid – Send kill signal to process (pid)

jobs – List all currently running jobs

dmesg | less –

dmesg | grep sdb –

tar -czf BackupFileneme.tar.gz /Folder – Backup a the /Folder and all the files it contains into a single gzipped, tar file (BackupFilename)

tar -xvfz BackupFileneme.tar.gz – Extract the gzipped, tar file (BackupFilename) to some other location on a hard drive

find / -perm +6000 -type f > SUID-GUID-bits-Set.txt – Search system for all SUID/GUID files

Useful Configuration Files

Shell Configuration files

    Per user configuration files
         ~/.bashrc
         ~/.profile

    Global configuration files
         /etc/bash.bashrc
         /etc/profile