Online Tools
Linux Commands - System Information
Command Code Notes
arch Display the processor architecture of the machine (1)
uname -m Display the processor architecture of the machine (2)
uname -r Display the kernel version in use
dmidecode -q Displays hardware system components -(SMBIOS / DMI)
hdparm -i /dev/hda List the architectural characteristics of a disk
hdparm -tT /dev/sda Perform a test read operation on a disk
cat /proc/cpuinfo Display information about CPU info
cat /proc/interrupts Display interrupts
cat /proc/meminfo Verify memory usage
cat /proc/swaps Shows which swaps are being used
cat /proc/version Show kernel version
cat /proc/net/dev Show network adapters and statistics
cat /proc/mounts Show loaded filesystems
lspci -tv List PCI devices
lsusb -tv Show USB devices
date Show system date
cal 2007 Show Calendar 2007
date 041217002007.00 Setting the Date and Time - Month Day Hour Minute Year. Seconds
clock -w Save time changes to BIOS
Linux Commands - System Shutdown( Shutting down, rebooting and logging off)
Command Code Explanation
shutdown -h now Shutdown System
init 0 Shut down the system
telinit 0 Shut down the system
shutdown -h hours:minutes & Shuts down the system at the scheduled time
shutdown -c Cancelling the scheduled shutdown of the system
shutdown -r now Reboot
reboot Reboot
logout Logout
Linux Commands - Files and Directories
Command Code Comment Description
cd /home Enter'/ home' directory'
cd .. Return to the previous directory
cd ../.. Returns to the previous two directories
cd Access to the personal master catalogue
cd ~user1 Go to your personal home directory
cd - Return to the last directory
pwd Show working path
ls Viewing files in a directory
ls -F Viewing files in a directory
ls -l Show file and directory details
ls -a Show hidden files
ls *[0-9]* Display file and directory names containing numbers
tree Displaying the tree structure of files and directories starting from the root directory
lstree Displaying the tree structure of files and directories starting from the root directory
mkdir dir1 Create a directory called'dir1' directory'
mkdir dir1 dir2 Creates two directories at the same time
mkdir -p /tmp/dir1/dir2 Creating a directory tree
rm -f file1 Delete a file called'file1' file'
rmdir dir1 Delete a directory called'dir1' directory'
rm -rf dir1 Delete a directory called'dir1' and delete its contents at the same time
rm -rf dir1 dir2 Delete two directories and their contents at the same time
mv dir1 new_dir Rename/move a directory
cp file1 file2 Copy a file
cp dir0/g' example.txt Replace multiple zeros with a single zero
cat -n file1 Marks the number of lines in a file
cat example.txt | awk 'NR%2==1' Delete all even lines in example.txt file
echo a b c | awk '{print $1}' View the first column of a line
echo a b c | awk '{print $1,$3}' View the first and third columns of a line
paste file1 file2 Merge the contents of two files or two columns
paste -d '+' file1 file2 Merge the contents of two files or two columns with a"+" Sort
sort file1 file2 Sort the contents of two files
sort file1 file2 | uniq Take out the union of two files( Keep only one copy of duplicate rows)
sort file1 file2 | uniq -u Delete the intersection and leave the rest of the rows.
sort file1 file2 | uniq -d Remove the intersection of two files( Leave only the files that exist in both files.)
comm -1 file1 file2 Compare the contents of two files and remove only'file1' Remove only the contents of the file that is contained in the file.
comm -2 file1 file2 Compare the contents of two files and remove only'file2' Included content
comm -3 file1 file2 Comparing the contents of two files removes only the parts that are common to both files.
Linux Commands - Character Setting and File Format Conversion
Command Code Explanation
dos2unix filedos.txt fileunix.txt Converts the format of a text file from MSDOS to UNIX.
unix2dos fileunix.txt filedos.txt Converts a text file from UNIX to MSDOS.
recode ..HTML < page.txt > page.html Convert a text file to html
recode -l | more Show all allowed conversion formats
Linux Commands - File System Analysis
Command Code Explanation of comments
badblocks -v /dev/hda1 Check for bad blocks on disk hda1
fsck /dev/hda1 Repair/check integrity of linux filesystem on disk hda1
fsck.ext2 /dev/hda1 Repair/check integrity of ext2 file system on disk hda1
e2fsck /dev/hda1 Repair/check integrity of ext2 file system on disk hda1
e2fsck -j /dev/hda1 Repair/check the integrity of the ext3 file system on disk hda1
fsck.ext3 /dev/hda1 Repair/check integrity of ext3 file system on hda1 disc
fsck.vfat /dev/hda1 Repair/check integrity of fat file system on hda1 disc
fsck.msdos /dev/hda1 Repair/check integrity of dos file system on hda1 disc
dosfsck /dev/hda1 Repair/check the integrity of the dos filesystem on disk hda1
Linux Command - Initialise a File System
Command Code Notes
mkfs /dev/hda1 Create a file system on hda1 partition
mke2fs /dev/hda1 Create a linux ext2 filesystem on hda1 partition
mke2fs -j /dev/hda1 Create a linux ext3 on partition hda1( logging) file system on hda1
mkfs -t vfat 32 -F /dev/hda1 Creating a FAT32 file system
fdformat -n /dev/fd0 Format a floppy disc
mkswap /dev/hda3 Creating a swap filesystem
Linux Commands - SWAP Filesystem
Command Code Explanation
mkswap /dev/hda3 Create a swap file system
swapon /dev/hda3 Enables a new swap file system
swapon /dev/hda2 /dev/hdb3 Enable two swap partitions
Linux Commands - Backup
Command Code Note Explanation
dump -0aj -f /tmp/home0.bak /home Makes a'/home' full backup of a directory
dump -1aj -f /tmp/home0.bak /home Makes an interactive backup of a'/home' interactive backup of a directory
restore -if /tmp/home0.bak Restore an interactive backup
rsync -rogpav --delete /home /tmp Synchronise both directories
rsync -rogpav -e ssh --delete /home ip_address:/tmp rsync over an SSH channel
rsync -az -e ssh --delete ip_addr:/home/public /home/local Sync a remote directory to a local directory via ssh and compression
rsync -az -e ssh --delete /home/local ip_addr:/home/public Sync a local directory to a remote directory via ssh and compression
dd bs=1M if=/dev/hda | gzip | ssh user@ip_addr 'dd of=hda.gz' Perform a backup of a local disc on a remote host via ssh
dd if=/dev/sda of=/tmp/file1 Backing up the contents of a disc to a file
tar -Puf backup.tar /home/user Perform an interactive backup of the'/home/user' directory interactively
( cd /tmp/local/ && tar c . ) | ssh -C user@ip_addr 'cd /home/share/ && tar x -p' Copying the contents of a directory to a remote directory via ssh
( tar c /home ) | ssh -C user@ip_addr 'cd /home/backup-home && tar x -p' Copy a local directory to a remote directory via ssh
tar cf - . | (cd /tmp/backup ; tar xf - ) Locally copy a directory to another location, preserving permissions and links.
find /home/user1 -name '*.txt' | xargs cp -av --target-directory=/home/backup/ --parents Find and copy all files ending with'.txt' endings to another directory
find /var/log -name '*.log' | tar cv --files-from=- | bzip2 > log.tar.bz2 Find all files ending in'.log' endings and make a bzip package.
dd if=/dev/hda of=/dev/fd0 bs=512 count=1 Make a copy of the MBR(Master Boot Record) contents to a floppy disc
dd if=/dev/fd0 of=/dev/hda bs=512 count=1 Restore MBR contents from a backup that has been saved to a floppy disc
Linux Commands - CD-ROM
Command Code Note Explanation
cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force Empties the contents of a rewritable disc
mkisofs /dev/cdrom > cd.iso Creates an iso image of the disc on the disk.
mkisofs /dev/cdrom | gzip > cd_iso.gz Creates a compressed iso image of a disc on a disk.
mkisofs -J -allow-leading-dots -R -V "Label CD" -iso-level 4 -o ./cd.iso data_cd Creates an iso image of a directory.
cdrecord -v dev=/dev/cdrom cd.iso Burn an ISO image file
gzip -dc cd_iso.gz | cdrecord dev=/dev/cdrom - Burn a compressed ISO image file
mount -o loop cd.iso /mnt/iso Mount an ISO image file
cd-paranoia -B Extract audio tracks from a CD disc to a wav file
cd-paranoia -- "-3" Extract tracks from a CD disc to a wav file (parameter -3)
cdrecord --scanbus Scan the bus to identify scsi channels
dd if=/dev/hdc | md5sum Verify the md5sum encoding of a device, e.g. a CD
Linux commands - network - (Ethernet and WIFI wireless)
Command code Notes
dhclient eth0 Enables the 'eth0' network device in dhcp mode.
ethtool eth0 Display traffic statistics for network card 'eth0'.
host www.example.com Find hostnames to resolve names and IP addresses and mirrors
hostname Display hostnames
ifconfig eth0 Display the configuration of an Ethernet card
ifconfig eth0 192.168.1.1 netmask 255.255.255.0 Controlling IP Addresses
ifconfig eth0 promisc Set 'eth0' to promiscuous mode for packet sniffing
ifdown eth0 Disable an 'eth0' network device
ifup eth0 Enable an 'eth0' network device
ip link show Show connection status of all network devices
iwconfig eth1 Display the configuration of a wireless card
iwlist scan Show wireless networks
mii-tool eth0 Show the connection status of 'eth0'
netstat -tup Show all enabled network connections and their PIDs
netstat -tup1 Show all listening network services on the system and their PIDs.
netstat -rn Display the routing table, similar to the "route -n" command.
nslookup www.example.com Find hostnames to resolve names and IP addresses and mirrors
route -n Show routing table
route add -net 0/0 gw IP Gateway Controlling Predefined Gateways
route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1 Controls static routes to network '192.168.0.0/16'.
route del 0/0 gw IP gateway Delete static routes
echo “1”> /proc/sys/net/ipv4/ip_foward Activate IP Forwarding
tcpdump tcp port 80 Show all HTTP loops
whois www.example.com Lookup in Whois database
Linux Commands - Microsoft Windows Network
Command Code Note Explanation
mount -t smbfs -o username=user,password=pass Mount a windows network share
nbtscan ip addr netbios name resolution
nmblookup -A ip addr netbios name resolution
smbclient -L ip addr/hostname Show remote share of a windows host
smbget -Rr smb: Download files from a windows host via smb like wget.
Linux Commands - IPTABLES(firewall)
Command Code Explanation
iptables -t filter -L Displays all links in the filter table
iptables -t nae -L Displays all links in the nat table
iptables -t filter -F Clears all rules based on the filter table
iptables -t nat -F Clears all rules based on the nat table
iptables -t filter -X Delete all links created by the user
iptables -t filter -A INPUT -p tcp --dport telnet -j ACCEPT Allow telnet access
iptables -t filter -A OUTPUT -p tcp --dport telnet -j DROP Block telnet access
iptables -t filter -A FORWARD -p tcp --dport pop3 -j ACCEPT Allow forwarding of POP3 connections on links
iptables -t filter -A INPUT -j LOG --log-prefix Record all packets blocked on the link
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE Set up a PAT (Port Address Translation) to mask outgoing packets at eth0
iptables -t nat -A POSTROUTING -d 192.168.0.1 -p tcp -m tcp --dport 22-j DNAT --to-destination 10.0.0.2:22 Divert packets destined for one host address to other hosts
Linux Commands - Monitoring and Debugging
Command Code Notes
free -m List RAM status in megabytes
kill -9 process id Force a process to shut down and end it
kill -1 process id Force a process to reload its configuration
last reboot Show reboot history
lsmod List the status of kernel modules
lsof -p process id List a list of files opened by a process
lsof /home/user1 List opened files in the given system paths
ps -eafw List linux tasks
ps -e -o pid,args --forest List linux tasks in a hierarchical way.
pstress Display processes in a tree view
smartctl -A /dev/hda Monitor the reliability of a hard disc device by enabling SMART.
smartctl -i /dev/hda Checks whether SMART is enabled for a hard disc device.
strace -c ls >/dev/null List system calls made and received by a process
strace -f -e open ls >/dev/null List library calls
tail /var/log/dmesg Display internal events during kernel boot
tail /val/log/messages Show system events
top List the linux tasks that use the most CPU resources
watch -nl ‘cat /proc/interrupts’ List real-time interrupts
Linux commands - other common commands
Command Code Notes
alias hh='history' Set an alias for the command history.
apropos ...keyword Make a list of commands with program keywords, especially useful if you only know what the program does and you don't remember the commands
chsh Changing shell commands
chsh --list-shells A good command for finding out if you have to connect remotely to another machine.
gpg -c filel Encrypt a file with GNU Privacy Guard
gpg filel.gpg Decrypt a file with GNU Privacy Guard.
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