Linux commands - system information
Command code Comment description
arch Display the machine's processor architecture (1)
uname -m Display the machine's processor architecture (2)
uname -r Display the kernel version in use
dmidecode -q Display hardware system components - (SMBIOS / DMI)
hdparm -i /dev/hda List the architectural features of a disk
hdparm -tT /dev/sda Perform a test read operation on the disk
cat /proc/cpuinfo Display CPU info information
cat /proc/interrupts Display interrupts
cat /proc/meminfo Check memory usage
cat /proc/swaps Display which swap is used
cat /proc/version Display the kernel version
cat /proc/net/dev Display network adapters and statistics
cat /proc/mounts Display loaded file systems
lspci -tv List PCI devices
lsusb -tv Display USB devices
date Display system date
cal 2007 Display the calendar for 2007
date 041217002007.00 Set date and time - month, day, hour, minute, year, second
clock -w Save time changes to BIOS
Linux commands - System shutdown (shutdown, reboot, and logout)
Command code Comment
shutdown -h now Shut down the system
init 0 Shut down the system
telinit 0 Shut down the system
shutdown -h hours:minutes & Schedule shutdown
shutdown -c Cancel scheduled shutdown
shutdown -r now Reboot
reboot Reboot
logout Logout
Linux commands - files and directories
Command code Comment
cd /home Go to '/ home' directory
cd .. Go back one level to the previous directory
cd ../.. Go back two levels to the previous directory
cd Go to one's home directory
cd ~user1 Go to one's home directory
cd - Go back to the last directory you were in
pwd Show working directory
ls View files in a directory
ls -F View files in a directory
ls -l Show detailed information about files and directories
ls -a Show hidden files
ls *[0-9]* Show file names and directory names that contain numbers
tree Show a tree of files and directories starting from the root directory
lstree Show a tree of files and directories starting from the root directory
mkdir dir1 Create a directory called 'dir1'
mkdir dir1 dir2 Create two directories at the same time
mkdir -p /tmp/dir1/dir2 Create a directory tree
rm -f file1 Delete a file called 'file1'
rmdir dir1 Delete a directory called 'dir1'
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 dir/* . Copy all files in a directory to the current working directory
cp -a /tmp/dir1 . Copy a directory to the current working directory
cp -a dir1 dir2 Copy a directory
ln -s file1 lnk1 Create a soft link to a file or directory
ln file1 lnk1 Create a physical link to a file or directory
touch -t 0712250000 file1 Modify the timestamp of a file or directory - (YYMMDDhhmm)
iconv -l List known encodings
iconv -f fromEncoding -t toEncoding inputFile > outputFile Change the encoding of a character
find . -maxdepth 1 -name *.jpg -print -exec convert Batch resize files in the current directory and send them to a thumbnail directory (needs conversion from ImageMagick)
Linux Commands - File Search
Command Code Comment Description
find / -name file1 Search for files and directories in the root file system starting at '/'
find / -user user1 Search for files and directories belonging to user 'user1'
find /home/user1 -name \*.bin Search for files ending with '.bin' in directory '/ home/user1'
find /usr/bin -type f -atime +100 Search for executable files that have not been used in the past 100 days
find /usr/bin -type f -mtime -10 Search for files created or modified in the past 10 days
find / -name \*.rpm -exec chmod 755 '{}' \; Search for files ending with '.rpm' and define their permissions
find / -xdev -name \*.rpm Search for files ending with '.rpm', ignoring removable devices such as CD-ROMs and Jiepian
locate \*.ps Find files ending with '.ps' - run 'updatedb' first Commands
whereis halt Show the location of a binary, source or man
which halt Show the full path to a binary or executable
Linux commands - mount a file system
Command code Comments
mount /dev/hda2 /mnt/hda2 Mount a disk called hda2 - make sure the directory '/ mnt/hda2' already exists
umount /dev/hda2 Unmount a disk called hda2 - exit from mount point '/ mnt/hda2' first
fuser -km /mnt/hda2 Force unmount when device is busy
umount -n /mnt/hda2 运行卸载操作而不写入 /etc/mtab 文件- 当文件为只读或当磁盘写满时非常有用
mount /dev/fd0 /mnt/floppy Mount a floppy disk
mount /dev/cdrom /mnt/cdrom Mount a cdrom or dvdrom
mount /dev/hdc /mnt/cdrecorder Mount a cdrw or dvdrom
mount /dev/hdb /mnt/cdrecorder Mount a cdrw or dvdrom
mount -o loop file.iso /mnt/cdrom Mount a file or ISO image file
mount -t vfat /dev/hda5 /mnt/hda5 Mount a Windows FAT32 file system
mount /dev/sda1 /mnt/usbdisk Mount a usb shortcut or flash device
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share Mount a windows network share
Linux commands - disk space
Command code Comments
df -h Show a list of mounted partitions
ls -lSr |more Sort files and directories by size
du -sh dir1 Estimate directory 'dir1' Used disk space'
du -sk * | sort -rn Show the size of files and directories in order of capacity
rpm -q -a --qf '%10{SIZE}t%{NAME}n' | sort -k1,1n 以大小为依据依次显示已安装的rpm包所使用的空间 (fedora, redhat类系统)
dpkg-query -W -f='${Installed-Size;10}t${Package}n' | sort -k1,1n 以大小为依据显示已安装的deb包所使用的空间 (ubuntu, debian类系统)
Linux commands - users and groups
Command code Comment
groupadd group_name Create a new user group
groupdel group_name Delete a user group
groupmod -n new_group_name old_group_name Rename a user group
useradd -c "Name Surname " -g admin -d /home/user1 -s /bin/bash user1 Create a user group belonging to the "admin" user grouphousehold
useradd user1 Create a new user
userdel -r user1 Remove a user ('-r' excludes home directory)
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1 Modify user attributes
passwd Change password
passwd user1 Modify a user's password (only allowed to be executed by root)
chage -E 2020-12-31 user1 Set user password expiration date
pwck Check '/etc/passwd' for file format and syntax fixes and existing users
grpck Check '/etc/passwd' for file format and syntax fixes and existing groups
newgrp group_name Log into a new group to change the default group for newly created files
Linux命令 — 文件的权限 - 使用 "+" 设置权限，使用 "-" 用于取消
command code Notes
ls -lh Show permissions
ls /tmp | pr -T5 -W$COLUMNS Divide the terminal into 5 columns for display
chmod ugo+rwx directory1 设置目录的所有人(u)、群组(g)以及其他人(o)以读（r ）、写(w)和执行(x)的权限
chmod go-rwx directory1 Remove the read, write, and execute permissions of the group (g) and others (o) on the directory
chown user1 file1 Change the owner attribute of a file
chown -R user1 directory1 Change the owner attributes of a directory and simultaneously change the attributes of all files in the directory
chgrp group1 file1 Change the group of a file
chown user1:group1 file1 Change the owner and group attributes of a file
find / -perm -u+s List all files controlled by SUID in a system
chmod u+s /bin/file1 设置一个二进制文件的 SUID 位 - 运行该文件的用户也被赋予和所有者同样的权限
chmod u-s /bin/file1 Disable the SUID bit of a binary file
chmod g+s /home/public Sets the SGID bit of a directory - similar to SUID, but for directories
chmod g-s /home/public Disable the SGID bit for a directory
chmod o+t /home/public Set the STIKY bit on a file - only allows the legitimate owner to delete the file
chmod o-t /home/public Disable the STIKY bit for a directory
Linux命令 — 文件的特殊属性 - 使用 "+" 设置权限，使用 "-" 用于取消
command code Notes
chattr +a file1 Only allowed to read and write files in append mode
chattr +c file1 Allow this file to be automatically compressed/decompressed by the kernel
chattr +d file1 The dump program will ignore this file when doing a file system backup
chattr +i file1 Files set to be immutable cannot be deleted, modified, renamed or linked to
chattr +s file1 Allow a file to be safely deleted
chattr +S file1 Once the application performs a write operation on this file, the system immediately writes the modified results to the disk.
chattr +u file1 If a file is deleted, the system will allow you to recover the deleted file later
lsattr Show special properties
Linux Commands — Packing and Compressing Files
command code Notes
bunzip2 file1.bz2 Unzip a file called 'file1.bz2'
bzip2 file1 Compress a file called 'file1'
gunzip file1.gz Unzip a file called 'file1.gz'
gzip file1 Compress a file called 'file1'
gzip -9 file1 maximum compression
rar a file1.rar test_file Create a package called 'file1.rar'
rar a file1.rar file1 file2 dir1 Compress 'file1', 'file2' and directory 'dir1' simultaneously
rar x file1.rar Unzip rar package
unrar x file1.rar Unzip rar package
tar -cvf archive.tar file1 Create an uncompressed tarball
tar -cvf archive.tar file1 file2 dir1 Create an archive file containing 'file1', 'file2' and 'dir1'
tar -tf archive.tar Display the contents of a package
tar -xvf archive.tar release a package
tar -xvf archive.tar -C /tmp Release the compressed package to the /tmp directory
tar -cvfj archive.tar.bz2 dir1 Create a compressed package in bzip2 format
tar -jxvf archive.tar.bz2 Decompress a compressed package in bzip2 format
tar -cvfz archive.tar.gz dir1 Create a compressed package in gzip format
tar -zxvf archive.tar.gz Decompress a compressed package in gzip format
zip file1.zip file1 Create a compressed package in zip format
zip -r file1.zip file1 file2 dir1 Compress several files and directories into a compressed package in zip format at the same time
unzip file1.zip Unzip a zip format compressed package
Linux commands - RPM packages - (Fedora, Redhat and similar systems)
command code Notes
rpm -ivh package.rpm Install an rpm package
rpm -ivh --nodeeps package.rpm Install an rpm package ignoring dependency warnings
rpm -U package.rpm Update an rpm package without changing its configuration file
rpm -F package.rpm Update an rpm package that is already installed
rpm -e package_name.rpm Delete an rpm package
rpm -qa Display all installed rpm packages in the system
rpm -qa | grep httpd Display all rpm packages containing "httpd" in their name
rpm -qi package_name Get special information about an installed package
rpm -qg "System Environment/Daemons" Display the rpm package of a component
rpm -ql package_name Display a list of files provided by an installed rpm package
rpm -qc package_name Display a list of configuration files provided by an installed rpm package
rpm -q package_name --whatrequires Display a list of dependencies on an rpm package
rpm -q package_name --whatprovides Display the volume occupied by an rpm package
rpm -q package_name --scripts Show scripts executed during installation/removal
rpm -q package_name --changelog Display the modification history of an rpm package
rpm -qf /etc/httpd/conf/httpd.conf Confirm which rpm package the given file is provided by
rpm -qp package.rpm -l Display a list of files provided by an rpm package that has not yet been installed
rpm --import /media/cdrom/RPM-GPG-KEY Import public key digital certificate
rpm --checksig package.rpm Confirm the integrity of an rpm package
rpm -qa gpg-pubkey Confirm the integrity of all installed rpm packages
rpm -V package_name 检查文件尺寸、 许可、类型、所有者、群组、MD5检查以及最后修改时间
rpm -Va Check all installed rpm packages on the system - use with caution
rpm -Vp package.rpm Confirm that an rpm package has not been installed yet
rpm2cpio package.rpm | cpio --extract --make-directories *bin* Run an executable file from an rpm package
rpm -ivh /usr/src/redhat/RPMS/`arch`/package.rpm Install a built package from an rpm source
rpmbuild --rebuild package_name.src.rpm Build an rpm package from an rpm source code
Linux command - YUM package upgrader - (Fedora, RedHat and similar systems)
command code Notes
yum install package_name Download and install an rpm package
yum localinstall package_name.rpm will install an rpm package, using your own software repository to resolve all dependencies for you
yum update package_name.rpm Update all rpm packages installed in the current system
yum update package_name Update an rpm packageDelete an rpm package
yum remove package_name List all packages installed on the current system
yum list Search for packages in the rpm repository
yum search package_name Clean rpm cache and delete downloaded packages
yum clean packages Remove all header files
yum clean headers Remove all cached packages and header files
yum clean all Linux commands - DEB packages (Debian, Ubuntu and similar systems)
command code
Notes Install/update a deb package
dpkg -i package.deb Remove a deb package from the system
dpkg -r package_name Display all installed deb packages in the system
dpkg -l Display all deb packages containing "httpd" in their name
dpkg -l | grep httpd Get information about a particular package that has been installed on the system
dpkg -s package_name Display the file list provided by a deb package that has been installed on the system
dpkg -L package_name Displays a list of files provided by a package that is not yet installed
dpkg --contents package.deb Confirm which deb package the given file is provided by
dpkg -S /bin/ping Linux Commands — APT Software Tools (Debian, Ubuntu and similar systems)
command code
Notes Install/update a deb package
apt-get install package_name Install/update a deb package from CD
apt-cdrom install package_name Upgrade packages in list
apt-get update Upgrade all installed software
apt-get upgrade Delete a deb package from the system
apt-get remove package_name Confirm that the dependent software repository is correct
apt-get check Clean cache from downloaded packages
apt-get clean Returns the package name containing the search string
apt-cache search searched-package Linux command — view file contents
command code
Notes View the contents of the file forward starting from the first byte
cat file1 View the contents of a file in reverse order starting from the last line
tac file1 View the contents of a long file
more file1 Similar to the 'more' command, but it allows reverse operations on files as well as forward operations
less file1 类似于 'more' 命令，但是它允许在文件中和正向操作一样的反向操作
head -2 file1 View the last two lines of a file
tail -2 file1 View content being added to a file in real time
tail -f /var/log/messages Linux Commands — Text Processing
command code
Notes Merge the detailed description text of one file and write the introduction to a new file
cat file1 | command( sed, grep, awk, grep, etc...) > result.txt Merge the detailed description text of a file and write the introduction to an existing file
cat file1 | command( sed, grep, awk, grep, etc...) >> result.txt Search for the keyword "Aug" in the file '/var/log/messages'
grep Aug /var/log/messages Search the file '/var/log/messages' for words starting with "Aug"
grep ^Aug /var/log/messages Select all lines containing numbers in the '/var/log/messages' file
grep [0-9] /var/log/messages Search the directory '/var/log' and subsequent directories for the string "Aug"
grep Aug -R /var/log/* Replace "string1" in the example.txt file with "string2"
sed 's/stringa1/stringa2/g' example.txt Remove all blank lines from example.txt file
sed '/^$/d' example.txt sed '/ *#/d; /^$/d' example.txt from example.txt
Remove all comments and blank lines from the file Merge the contents of upper and lower cells
echo 'esempio' | tr '[:lower:]' '[:upper:]' Exclude the first line from the file example.txt
sed -e '1d' result.txt View lines containing only the word "string1"
sed -n '/stringa1/p' Remove whitespace characters at the end of each line
sed -e 's/ *$//' example.txt Remove only the word "string1" from the document and keep everything else
sed -e 's/stringa1//g' example.txt View content from line 1 to line 5
sed -n '1,5p;5q' example.txt Look at line 5
sed -n '5p;5q' example.txt Replace multiple zeros with a single zero
sed -e 's/00*/0/g' example.txt Indicates the number of lines in the file
cat -n file1 Delete all even lines in example.txt file
cat example.txt | awk 'NR%2==1' View the first column of a row
echo a b c | awk '{print $1}' Look at the first and third columns of a row
echo a b c | awk '{print $1,$3}' Merge the contents of two files or columns
paste file1 file2 Merge the contents of two files or two columns, using "+" to distinguish them.
paste -d '+' file1 file2 Sort the contents of two files
sort file1 file2 Take the union of two files (only one copy of duplicate lines is kept)
sort file1 file2 | uniq Remove intersection, leaving other rows
sort file1 file2 | uniq -u Take out the intersection of two files (leaving only files that exist in both files)
sort file1 file2 | uniq -d Compare the contents of two files and delete only the contents contained in 'file1'
comm -1 file1 file2 Compare the contents of two files and delete only the contents contained in 'file2'
comm -2 file1 file2 Compare the contents of two files and delete only the parts common to both files
comm -3 file1 file2 Linux commands - character settings and file format conversion
command code
Notes Convert the format of a text file from MSDOS to UNIX
dos2unix filedos.txt fileunix.txt Convert the format of a text file from UNIX to MSDOS
unix2dos fileunix.txt filedos.txt Convert a text file to html
recode ..HTML < page.txt> page.html Show all allowed conversion formats
recode -l | more Linux Commands — File System Analysis
command code
Notes Check for bad blocks on disk hda1
badblocks -v /dev/hda1 Repair/check integrity of linux file system on hda1 disk
fsck /dev/hda1 Repair/check integrity of ext2 file system on hda1 disk
fsck.ext2 /dev/hda1 Repair/check integrity of ext2 file system on hda1 disk
e2fsck /dev/hda1 Repair/check integrity of ext3 file system on hda1 disk
e2fsck -j /dev/hda1 Repair/check integrity of ext3 file system on hda1 disk
fsck.ext3 /dev/hda1 Repair/check integrity of fat file system on hda1 disk
fsck.vfat /dev/hda1 Repair/check integrity of dos file system on hda1 disk
fsck.msdos /dev/hda1 Repair/check integrity of dos file system on hda1 disk
dosfsck /dev/hda1 Linux command — initialize a file system
command code
Notes Create a file system on the hda1 partition
mkfs /dev/hda1 Create a linux ext2 file system on the hda1 partition
mke2fs /dev/hda1 Create a linux ext3 (journaled) file system in the hda1 partition
mke2fs -j /dev/hda1 Create a FAT32 file system
mkfs -t vfat 32 -F /dev/hda1 Format a floppy disk
fdformat -n /dev/fd0 Create a swap file system
mkswap /dev/hda3 Linux Commands — SWAP File System
command code
Notes Create a swap file system
mkswap /dev/hda3 Enable a new swap file system
swapon /dev/hda3 Enable two swap partitions
swapon /dev/hda2 /dev/hdb3 Linux Commands — Backup
command code
Notes Make a '/home' directory full backup
dump -0aj -f /tmp/home0.bak /home Make an interactive backup of the '/home' directory
dump -1aj -f /tmp/home0.bak /home Restoring an interactive backup
restore -if /tmp/home0.bak Synchronize directories on both sides
rsync -rogpav --delete /home /tmp rsync over SSH channel
rsync -rogpav -e ssh --delete /home ip_address:/tmp Sync a remote directory to a local directory via ssh and compression
rsync -az -e ssh --delete ip_addr:/home/public /home/local Sync local directory to remote directory via ssh and compression
rsync -az -e ssh --delete /home/local ip_addr:/home/public Perform a local disk backup operation on the remote host through ssh
dd bs=1M if=/dev/hda | gzip | ssh user@ip_addr 'dd of=hda.gz' Back up disk contents to a file
dd if=/dev/sda of=/tmp/file1 Perform an interactive backup of the '/home/user' directory
tar -Puf backup.tar /home/user Copy the contents of a directory to a remote directory via ssh
( cd /tmp/local/ && tar c . ) | ssh -C user@ip_addr 'cd /home/share/ && tar x -p' Copy a local directory in a remote directory via ssh
( tar c /home ) | ssh -C user@ip_addr 'cd /home/backup-home && tar x -p' Copy a directory locally to another place, retaining original permissions and links
tar cf - . | (cd /tmp/backup ; tar xf - ) Find and copy all files ending with '.txt' from one directory to another
find /home/user1 -name '*.txt' | xargs cp -av --target-directory=/home/backup/ --parents 从一个目录查找并复制所有以 '.txt' 结尾的文件到另一个目录
find /var/log -name '*.log' | tar cv --files-from=- | bzip2 > log.tar.bz2 Perform an action to copy the contents of MBR (Master Boot Record) to a floppy disk
dd if=/dev/hda of=/dev/fd0 bs=512 count=1 Recover MBR contents from backup that has been saved to floppy disk
dd if=/dev/fd0 of=/dev/hda bs=512 count=1 Linux Commands — CD
command code
Notes Erase the contents of a rewritable disc
cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force Create an iso image file of the CD on the disk
mkisofs /dev/cdrom > cd.iso Create a compressed CD iso image file on the disk
mkisofs /dev/cdrom | gzip > cd_iso.gz Create an iso image file of a directory
mkisofs -J -allow-leading-dots -R -V "Label CD" -iso-level 4 -o ./cd.iso data_cd Burn an ISO image file
cdrecord -v dev=/dev/cdrom cd.iso Burn a compressed ISO image file
gzip -dc cd_iso.gz | cdrecord dev=/dev/cdrom - Mount an ISO image file
mount -o loop cd.iso /mnt/iso Rip audio tracks from a CD to wav files
cd-paranoia -B Rip audio tracks from a CD to a wav file (parameter -3)
cd-paranoia -- "-3" Scan bus to identify scsi channel
cdrecord --scanbus Verify the md5sum encoding of a device, such as a CD
dd if=/dev/hdc | md5sum Linux Commands - Network - (Ethernet and WIFI Wireless)
command code
Notes Enable 'eth0' network device in dhcp mode
dhclient eth0 Display traffic statistics of network card ‘eth0’
ethtool eth0 Find hostnames to resolve names and IP addresses and mirrors
host www.example.com show hostname
hostname Display the configuration of an Ethernet card
ifconfig eth0 Control IP address
ifconfig eth0 192.168.1.1 netmask 255.255.255.0 Set 'eth0' to promiscuous mode to sniff packets (sniffing)
ifconfig eth0 promisc Disable an 'eth0' network device
ifdown eth0 Enable an 'eth0' network device
ifup eth0 Display the connection status of all network devices
ip link show Display the configuration of a wireless network card
iwconfig eth1 Show wireless networks
iwlist scan Display the connection status of 'eth0'
mii-tool eth0 Show all enabled network connections and their PIDs
netstat -tup Display all listening network services in the system and their PIDs
netstat -tup1 Display the routing table, similar to the "route -n" command
netstat -rn Find hostnames to resolve names and IP addresses and mirrors
nslookup www.example.com show routing table
route -n Control default gateway
route add -net 0/0 gw IP Gateway Control static route to network '192.168.0.0/16'
route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1 Delete static route
route del 0/0 gw IP gateway Activate IP forwarding
echo “1”> /proc/sys/net/ipv4/ip_foward Show all HTTP loopbacks
tcpdump tcp port 80 Search in Whois database
whois www.example.com Linux Commands — Microsoft Windows Networking
command code
Notes Mount a windows network share
mount -t smbfs -o username=user,password=pass //WinClient/share/mnt/share netbios name resolution
nbtscan ip addr netbios name resolution
nmblookup -A ip addr Display remote shares of a windows host
smbclient -L ip addr/hostname Like wget, you can download files from a windows host via smb
smbget -Rr smb://ip addr/share Linux command — IPTABLES(firewall)
command code
Notes Show all links in the filter table
iptables -t filter -L Display all links in the nat table
iptables -t nae -L Clean up all rules based on filter table
iptables -t filter -F Clean up all rules based on NAT table
iptables -t nat -F Delete all links created by user
iptables -t filter -X Allow telnet access
iptables -t filter -A INPUT -p tcp --dport telnet -j ACCEPT Block telnet access
iptables -t filter -A OUTPUT -p tcp --dport telnet -j DROP Allow POP3 connections on forwarding links
iptables -t filter -A FORWARD -p tcp --dport pop3 -j ACCEPT Record blocked packets on all links
iptables -t filter -A INPUT -j LOG --log-prefix Set up a PAT (Port Address Translation) on eth0 to mask outgoing packets
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE Forward packets destined for one host address to other hosts
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 Linux commands — monitoring and debugging
command code
Notes List RAM status in megabytes
free -m Force close the process and end it
kill -9 process id Force a process to reload its configuration
kill -1 process id Show restart history
last reboot Kernel module that lists status
lsmod List a list of files opened by a process
lsof -p process id List of open files in the given system path
lsof /home/user1 List linux tasks
ps -eafw List linux tasks in a hierarchical manner
ps -e -o pid,args --forest Display program in tree view
pstress Monitor the reliability of hard drive devices by enabling SMART
smartctl -A /dev/hda Check whether SMART is enabled on a hard disk device
smartctl -i /dev/hda List system calls made and use a process to receive them
strace -c ls >/dev/null List library calls
strace -f -e open ls >/dev/null Display internal events during kernel boot process
tail /var/log/dmesg Show system events
tail /val/log/messages List the Linux tasks that use the most CPU resources
top List real-time interrupts
watch -nl ‘cat /proc/interrupts’ Linux commands — other commonly used commands
command code
Notes Set an alias for the command history
alias hh='history' Make a list of commands including program keywords. This is especially useful when you only know what the program does but don’t remember the commands.
apropos ...keyword Change shell command
chsh Nice command to know if you have to connect remotely to another machine
chsh --list-shells Encrypt a file with GNU Privacy Guard
gpg -c filel Decrypt a file with GNU Privacy Guard
gpg filel.gpg 用GNU Privacy Guard解密一个文件

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