Liste de commandes à connaitre (a)

Disk Space
df -h show list of partitions mounted
ls -lSr |more show size of the files and directories ordered by size
du -sh dir1 estimate space used by directory 'dir1'
du -sk * | sort -rn show size of the files and directories sorted by size
rpm -q -a --qf '%10{SIZE}t%{NAME}n' | sort -k1,1n show space used by rpm packages installed sorted by size (fedora, redhat and like)
dpkg-query -W -f='${Installed-Size;10}t${Package}n' | sort -k1,1n show space used by deb packages installed sorted by size (ubuntu, debian and like)

Users and Groups
groupadd group_name create a new group
groupdel group_name delete a group
groupmod -n new_group_name old_group_name rename a group
useradd -c "Name Surname " -g admin -d /home/user1 -s /bin/bash user1 create a new user belongs "admin" group
useradd user1 create a new user
userdel -r user1 delete a user ( '-r' eliminates home directory)
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1 change user attributes
passwd change password
passwd user1 change a user password (only by root)
chage -E 2005-12-31 user1 set deadline for user password
pwck check correct syntax and file format of '/etc/passwd' and users existence
grpck check correct syntax and file format of '/etc/group' and groups existence
newgrp group_name log in to a new group to change default group of newly created files

Permits on Files (use "+" to set permissions and "-" to remove)
ls -lh show permits
ls /tmp | pr -T5 -W$COLUMNS divide terminal into 5 columns
chmod ugo+rwx directory1 set permissions reading (r), write (w) and (x) access to users owner (u) group (g) and others (o)
chmod go-rwx directory1 remove permits reading (r), write (w) and (x) access to users group (g) and others (or
chown user1 file1 change owner of a file
chown -R user1 directory1 change user owner of a directory and all the files and directories contained inside
chgrp group1 file1 change group of files
chown user1:group1 file1 change user and group ownership of a file
find / -perm -u+s view all files on the system with SUID configured
chmod u+s /bin/file1 set SUID bit on a binary file - the user that running that file gets same privileges as owner
chmod u-s /bin/file1 disable SUID bit on a binary file
chmod g+s /home/public set SGID bit on a directory - similar to SUID but for directory
chmod g-s /home/public disable SGID bit on a directory
chmod o+t /home/public set STIKY bit on a directory - allows files deletion only to legitimate owners
chmod o-t /home/public disable STIKY bit on a directory

Special Attributes on files (use "+" to set permissions and "-" to remove)
chattr +a file1 allows write opening of a file only append mode
chattr +c file1 allows that a file is compressed / decompressed automatically by the kernel
chattr +d file1 makes sure that the program ignores Dump the files during backup
chattr +i file1 makes it an immutable file, which can not be removed, altered, renamed or linked
chattr +s file1 allows a file to be deleted safely
chattr +S file1 makes sure that if a file is modified changes are written in synchronous mode as with sync
chattr +u file1 allows you to recover the contents of a file even if it is canceled
lsattr show specials attributes

Archives and compressed files
bunzip2 file1.bz2 decompress a file called 'file1.bz2'
bzip2 file1 compress a file called 'file1'
gunzip file1.gz decompress a file called 'file1.gz'
gzip file1 compress a file called 'file1'
gzip -9 file1 compress with maximum compression
rar a file1.rar test_file create an archive rar called 'file1.rar'
rar a file1.rar file1 file2 dir1 compress 'file1', 'file2' and 'dir1' simultaneously
rar x file1.rar decompress rar archive
unrar x file1.rar decompress rar archive
tar -cvf archive.tar file1 create a uncompressed tarball
tar -cvf archive.tar file1 file2 dir1 create an archive containing 'file1', 'file2' and 'dir1'
tar -tf archive.tar show contents of an archive
tar -xvf archive.tar extract a tarball
tar -xvf archive.tar -C /tmp extract a tarball into / tmp
tar -cvfj archive.tar.bz2 dir1 create a tarball compressed into bzip2
tar -xvfj archive.tar.bz2 decompress a compressed tar archive in bzip2
tar -cvfz archive.tar.gz dir1 create a tarball compressed into gzip
tar -xvfz archive.tar.gz decompress a compressed tar archive in gzip
zip file1.zip file1 create an archive compressed in zip
zip -r file1.zip file1 file2 dir1 compress in zip several files and directories simultaneously
unzip file1.zip decompress a zip archive

RPM Packages ( Fedora, Red Hat and like)
rpm -ivh package.rpm install a rpm package
rpm -ivh --nodeps package.rpm install a rpm package ignoring dependencies requests
rpm -U package.rpm upgrade a rpm package without changing configuration files
rpm -F package.rpm upgrade a rpm package only if it is already installed
rpm -e package_name.rpm remove a rpm package
rpm -qa show all rpm packages installed on the system
rpm -qa | grep httpd show all rpm packages with the name "httpd"
rpm -qi package_name obtain information on a specific package installed
rpm -qg "System Environment/Daemons" show rpm packages of a group software
rpm -ql package_name show list of files provided by a rpm package installed
rpm -qc package_name show list of configuration files provided by a rpm package installed
rpm -q package_name --whatrequires show list of dependencies required for a rpm packet
rpm -q package_name --whatprovides show capability provided by a rpm package
rpm -q package_name --scripts show scripts started during installation / removal
rpm -q package_name --changelog show history of revisions of a rpm package
rpm -qf /etc/httpd/conf/httpd.conf verify which rpm package belongs to a given file
rpm -qp package.rpm -l show list of files provided by a rpm package not yet installed
rpm --import /media/cdrom/RPM-GPG-KEY import public-key digital signature
rpm --checksig package.rpm verify the integrity of a rpm package
rpm -qa gpg-pubkey verify integrity of all rpm packages installed
rpm -V package_name check file size, permissions, type, owner, group, MD5 checksum and last modification
rpm -Va check all rpm packages installed on the system - use with caution
rpm -Vp package.rpm verify a rpm package not yet installed
rpm2cpio package.rpm | cpio --extract --make-directories *bin* extract executable file from a rpm package
rpm -ivh /usr/src/redhat/RPMS/`arch`/package.rpm install a package built from a rpm source
rpmbuild --rebuild package_name.src.rpm build a rpm package from a rpm source

YUM packages updater (Fedora, RedHat and like)
yum install package_name download and install a rpm package
yum localinstall package_name.rpm That will install an RPM, and try to resolve all the dependencies for you using your repositories.
yum update update all rpm packages installed on the system
yum update package_name upgrade a rpm package
yum remove package_name remove a rpm package
yum list list all packages installed on the system
yum search package_name find a package on rpm repository
yum clean packages clean up rpm cache erasing downloaded packages
yum clean headers remove all files headers that the system uses to resolve dependency
yum clean all remove from the cache packages and headers files

DEB packages (Debian, Ubuntu and like)
dpkg -i package.deb install / upgrade a deb package
dpkg -r package_name remove a deb package from the system
dpkg -l show all deb packages installed on the system
dpkg -l | grep httpd show all deb packages with the name "httpd"
dpkg -s package_name obtain information on a specific package installed on system
dpkg -L package_name show list of files provided by a package installed on system
dpkg --contents package.deb show list of files provided by a package not yet installed
dpkg -S /bin/ping verify which package belongs to a given file

APT packages updater (Debian, Ubuntu e like)
apt-get install package_name install / upgrade a deb package
apt-cdrom install package_name install / upgrade a deb package from cdrom
apt-get update update the package list
apt-get upgrade upgrade all of the installed packages
apt-get remove package_name remove a deb package from system
apt-get check verify correct resolution of dependencies
apt-get clean clean up cache from packages downloaded
apt-cache search searched-package returns list of packages which corresponds string "searched-packages"

View file content
cat file1 view the contents of a file starting from the first row
tac file1 view the contents of a file starting from the last line
more file1 view content of a file along
less file1 similar to 'more' command but which allows backward movement in the file as well as forward movement
head -2 file1 view first two lines of a file
tail -2 file1 view last two lines of a file
tail -f /var/log/messages view in real time what is added to a file