View source for Linux commands

From Organic Design

← Linux commands

You do not have permission to edit this page, for the following reason:

---

You can view and copy the source of this page.

{{info|This is the start of a list of useful Linux shell commands (generally "one liners") we use a lot}} === Debian package management === The package management system used on [[Debian]] and the "downstream" distros based on it such as [[Ubuntu]] and [[Linux Mint|Mint]]. ==== Searching for an installed package ==== Use dpkg and grep; <source lang="bash"> dpkg -l | grep java </source> will list all installed packages and filter to only those with "java" in the name ==== Searching for installable packages ==== apt-cache performs a variety of operations on APT´s package cache <source lang="bash"> apt-cache search java </source> lists all packages in the cache with java in the name that are installable == SSH & SCP == See also [[SSH]] for more specific uses. === Screen === Screen is an essential utility to use during an SSH session over dodgy connections that can drop or when doing something mission-critical. Just use the '''screen''' command without any parameters and another shell session will start (if you ''exit'' you'll be back in the original shell session again). This new shell session will remain active even if the connection drops. To get back into the session again later, use '''screen -R'''. There are many other options for using multiple ''screen'' sessions and multiple windows onto a single session etc, see this [https://tournasdimitrios1.wordpress.com/2010/11/04/linux-the-screen-command-a-must-for-ssh/ screen cheatsheet] for more details. '''Note:''' One annoying issue with ''screen'' is that the normal scroll-back doesn't work, but you can user ''CTRL+A'' then ''ESC'' to activate "copy mode" which then allows you to scroll back using the cursor keys or page up/down. To exit "copy mode" use ESC again. === Basic SCP syntax === Example of sending a file to a remote server: <source lang="bash"> scp -P 2222 /my/local/file.txt USER@example.com:/home/USER </source> Example of retrieving a file from a remote server: <source lang="bash"> scp -P 2222 USER@example.com:/home/USER/file.txt ./ </source> ''Note using port forwarding for commonly accessed sites you can define non standard ports in your <code>.ssh/config</code> so you never need to explicitly state them above.'' === Recovering from an interrupted transfer === This ability is included natively in Linux and used to be very useful for splitting large backups up so they could fit onto small media such as floppy disks. But there's one time when it's very useful nowadays too which is when a large file transfer gets interupted and there's no option for continuation such as when using SCP. When this happens, go onto the target machine, check how many bytes were transferred of the target file and rename it to "xaa". Then on the local machine, do the following command to split the source file into two parts, the first being of the size of the number of bytes that have already been transferred (in this example 1234567 bytes). <source lang="bash"> split -b 1234567 foo.tar.gz </source> The resulting files are called "xaa" and "xab", and the latter is the containing the remaining content that needs to be transferred to the target server. Once you've transferred it across, you can then join the two files (remember you renamed the first part to "xaa" so there's no need to transfer that) together using ''cat'' as follows, and then remove all the ''xa*'' files from noth source and target servers. <source lang="bash"> cat xa* > foo.tar.gz </source> === Tar pipes === <source lang="bash"> ## From a local to remote machine tar -zcvf - directory | ssh remote 'cd somewhere; tar -zxvf -' ## From remote machine to local machine ssh remote 'cd somewhere; tar -zcvf - directory' | tar -zxf - ## remote tar and pipe to tgz ssh remote 'cd somewhere; tar -zcf - directory' | cat - > directory.tar.gz </source> === Port-forwarding with SSH === {{:SSH}} == Files & Devices == *[https://www.digitalocean.com/community/tutorials/how-to-partition-and-format-storage-devices-in-linux Partitioning and formatting] === Clear the contents of a file === <source lang="bash"> > /path/to/file </source> === List all the storage devices and partitions attached to the system (even if they're unformatted or unmounted) === <source lang="bash"> cat /proc/partitions </source> To check what filesystem a device has on it use ''file'', e.g. <source lang="bash"> file -s /dev/sda1 </source> === Get the size of a directory and its contents === <source lang="bash"> du -sh /home/foo </source> Use this more specific version to find the size of a users Maildir folder: <source lang="bash"> du -sh /home/*/Maildir|sed 's|/home/||'|sed 's|/Maildir||' </source> Here's another version of ''du'' that accounts for dotfiles and sorts the results: <source lang="bash"> du -sch .[!.]* * | sort -h </source> === Search for file content recursively === Here's an example looking for a phrase within a specific file type recursively through a directory structure, and printing the file names and line numbers of the resulting matches. <source lang="bash"> grep -rn "Foo" *.php </source> There are other tips at [http://stackoverflow.com/questions/316590/how-do-you-use-cat-recursively stackoverflow.com]. === Search for file content recursively and tar === <source lang="bash"> ## Find and tar find . -name "*.R" -print0 | xargs -0 tar -cvf Rfiles.tar ## check contents tar -tvf Rfiles.tar ## Find and tar.gz find . -name "*.R" -print0 | xargs -0 tar -zcvf Rfiles.tar.gz ## check contents tar -ztvf Rfiles.tar.gz </source> === Search for file by name recursively === <source lang="bash"> find . -name "*.R" </source> === Count occurrences of a word in a file or files === <source lang="bash"> grep -roh "WORD" file*.txt | wc - </source> === Count the number of lines in a file or output === <source lang="bash"> wc -l <FILE> cat <FILE> grep foo | wc -l </source> === Search and replace content in files === You could also use find and sed, but I find that this little line of perl works nicely. <source lang="bash"> perl -pi -w -e 's/SEARCH/REPLACE/g;' *.php </source> *-e means execute the following line of code. *-i means edit in-place *-w write warnings *-p loop EXTS="7z t7z" === Search for files that contain the windows BOM character (&amp;#65279;) === Windows editors often add a BOM character to the beginning of UTF-8 encoded text files, these cause a lot of trouble for many types of scripts such as PHP and the problem can be very hard to track down. This short shell one-liner I found [http://stackoverflow.com/questions/204765/elegant-way-to-search-for-utf-8-files-with-bom here] searches the current directory recursively showing what files have a BOM, you can then use a decent editor like [[Geany]] to remove them. <source lang="bash"> grep -rlI $'\xEF\xBB\xBF' . </source> === Mass renaming === '''mmv''' is a mass move/copy/renaming tool that uses standard wildcards to perform its functions. According to the manual the “;” wildcard is useful for matching files at any depth in the directory tree (ie it will go below the current directory, recursively). ;Example: {{code|mmv \*.JPG \#1.jpg }} The first pattern matches anything with a “.JPG” and renames each file (the “#1” matches the first wildcard) to “.jpg”. Each time you use a \(wildcard) you can use a #x to get that wildcard. Where x is a positive number starting at 1. Copied off: http://tldp.org/LDP/GNU-Linux-Tools-Summary/html/mass-rename.html === Compare two directory structures for differences === This is very handy if you need to know if two directory structures are the same or not including file content. It uses the ''diff'' command with the ''r'' switch to work recursively and the ''x'' switch to allow skipping of the ''.svn'' directories. <source lang="bash"> diff -qrx .svn DIR1 DIR2 </source> === Mount a .iso and .img files === See [http://www.cyberciti.biz/tips/how-to-mount-iso-image-under-linux.html this] for ISO files and [https://askubuntu.com/questions/236263/browse-img-without-mounting this] for IMG files. === Mount a USB stick === If you don't know the device name of the stick, plug it in and find it with the following: <source lang="bash"> dmesg |grep SCSI </source> Then mount the first partition, <source lang="bash"> mkdir -p ~/memstick mount -t vfat -o rw,users /dev/sdX1 ~/memstick </source> === Clone a device === Remember that this is a very low-level operation and so if you're cloning a live partition you may end up with partially written files or other corruption issues on the destination. Stop as many services as you can first, do an ''fsck'' afterwards and manually copy any directories that had issues. <source>dd if=/dev/sda of=/dev/sdb bs=32M</source> A good way to find more information about the devices first, for example if you have a number of unformatted devices of the same size and need more specific information about the hardware, is to use the '''lsscsi'' command which gives the following sample output: <source> [0:0:0:0] disk AMCC 9650SE-2LP DISK 4.10 /dev/sdb [1:0:0:0] disk ATA Hitachi HUA72201 JP4O /dev/sda [2:0:0:0] disk ATA TOSHIBA MG03ACA1 FL1A /dev/sdc </source> The ''sdb'' and ''sdc'' devices look identical with commands such as ''lsblk'' or ''fdisk -l'', but one of the is a RAID pair and the other just a normal drive. '''See also:''' [[Clone a live partition over SSH]] === Changing device UUIDs === It may sometimes be useful to change the UUIDs of partitions such as when they've been cloned with a low-level method like ''dd''. '''Note:''' the disk identifier should also be changed which you can do with ''fdisk'' from the e'''x'''pert menu. Check what devices and UUIDs you have in the system: <source> # blkid /dev/sda1: UUID="bc459b13-3aad-4017-a68b-ce8ab36275e1" SEC_TYPE="ext2" TYPE="ext3" /dev/sda2: UUID="86ce60b7-ad4a-44aa-88e2-2aefd5c6c396" TYPE="swap" /dev/sda3: UUID="b56d82f7-5817-4a52-9763-0b38aa360e2b" TYPE="ext4" /dev/sdc1: UUID="81d40a02-8019-4c1f-afb8-fb41d117c6d1" TYPE="ext3" /dev/sdc2: UUID="c57f1400-129a-402a-90f1-820a22c6a2fe" TYPE="swap" /dev/sdc3: UUID="c23ab65a-c32f-41e3-bd31-51ed563e0099" TYPE="ext4" </source> or: <source> # ls -l /dev/disk/by-uuid/ total 0 lrwxrwxrwx 1 root root 10 Sep 2 12:10 81d40a02-8019-4c1f-afb8-fb41d117c6d1 -> ../../sdc1 lrwxrwxrwx 1 root root 10 Sep 2 12:10 86ce60b7-ad4a-44aa-88e2-2aefd5c6c396 -> ../../sda2 lrwxrwxrwx 1 root root 10 Sep 2 12:10 b56d82f7-5817-4a52-9763-0b38aa360e2b -> ../../sda3 lrwxrwxrwx 1 root root 10 Sep 2 12:10 bc459b13-3aad-4017-a68b-ce8ab36275e1 -> ../../sda1 lrwxrwxrwx 1 root root 10 Sep 2 12:10 c23ab65a-c32f-41e3-bd31-51ed563e0099 -> ../../sdc3 lrwxrwxrwx 1 root root 10 Sep 2 12:27 c57f1400-129a-402a-90f1-820a22c6a2fe -> ../../sdc2 </source> Check what swap partitions you have: <source> # cat /proc/swaps Filename Type Size Used Priority /dev/sda2 partition 3999740 0 -1 </source> Create a new UUID and assign it to and ext parition: <source> # uuidgen 81d40a02-8019-4c1f-afb8-fb41d117c6d1 #tune2fs /dev/sdb1 -U 81d40a02-8019-4c1f-afb8-fb41d117c6d1 </source> Do the same for a swap partition: <source> # uuidgen 86ce60b7-ad4a-44aa-88e2-2aefd5c6c396 # swapoff /dev/sda2 # mkswap -U 86ce60b7-ad4a-44aa-88e2-2aefd5c6c396 /dev/sda2 Setting up swapspace version 1, size = 3999740 KiB no label, UUID=86ce60b7-ad4a-44aa-88e2-2aefd5c6c396 </source> === Updating device partition tables without rebooting === *partprobe /dev/sdx *partx -u /dev/sdx *echo 1 > /sys/block/sdX/device/rescan *check partition information before and after with ''cat /proc/partitions'' === Downloading from google drive in shell === Thanks to [https://unix.stackexchange.com/questions/136371/how-to-download-a-folder-from-google-drive-using-terminal#148674 FrankerZ] for this! The first command outputs a code which you put into the second command. <source lang="bash"> wget --save-cookies cookies.txt --keep-session-cookies --no-check-certificate 'https://docs.google.com/uc?export=download&id={!FILEID!}' -O- | sed -rn 's/.*confirm=([0-9A-Za-z_]+).*/Code: \1\n/p' </source> <source lang="bash"> wget --load-cookies cookies.txt 'https://docs.google.com/uc?export=download&confirm={!CODE_FROM_ABOVE!}&id={!FILEID!}' -O {!FILENAME!} </source> == Image manipulation == === Resizing JPG's and changing quality setting === The first line shows how to reduce and image to 25% and quality to 50% adding "_resized" to the results filename. The second command uses Perl to apply this same command to all JPG's in the current directory. <source lang="bash"> convert foo.jpg -resize 25% -quality 50% foo_resized.jpg perl -e 'for (glob "*.jpg") { $img = $_; s/(....)$/_resized$1/; qx "convert \'$img\' -resize 25% -quality 50% \'$_\'"; }' </source> This command rotates, normalises, greyscales and sets the output quality of set of an image: <source lang="bash"> convert FILE -normalize -set colorspace Gray -separate -average -resize 50% -rotate "-90" -quality 75% OUT.JPG </source> === Apply an opaque background of a specified colour to a directory of transparent PNG's === *This command requires ImageMagick to be installed *It loops through all PNG's in the CWD and puts them in a directory called ''processed'' which must exist <source lang="bash"> perl -e 'qx "convert $_ -background #ff00ff -flatten foo/$_" for glob "*.png"' </source> == Audio & Video == === avconv (ffmpeg) === '''Note:''' Many operating systems including Ubuntu are now using the [http://libav.org/ libav] fork of ''ffmpeg'' now which means you should use the '''avconv''' command instead. The following converts a ''.wav'' file to an ''mp3'': <source lang="bash"> ffmpeg -i foo.wav foo.mp3 </source> Here's a more complicated example which converts ''mp4'' video into ''mp3'' audio at a lower quality with only one channel at 11KHz and 32kbps. <source lang="bash"> ffmpeg -i foo.mp4 -acodec libmp3lame -ab 16k -ar 11025 -ac 1 foo.mp3 </source> To do a whole directory you could do this: <source lang="bash"> perl -e 'qx "ffmpeg -i $_ $_.mp3" for glob "*.wav"' </source> Or a little more complex; a whole directory with a proper name change accounting for names with spaces in them. This <source lang="bash"> perl -e 'for (glob "*.mp4") { $i=$_; s/.mp3$/.converted.wav/; qx "ffmpeg -i \"$i\" \"$_\"" }' </source> Use the following commands to extract a small (5 seconds in this example) snippet out of a video (the -ar switch is only needed for outputting to flv I think). <source lang="bash"> ffmpeg -i "foo.avi" -ss 00:10:10 -t 5 -ar 22050 "foo.flv" </source> '''See also:''' *[[Simple video streaming with ffserver]] *[[Converting microarray images]] for bash/imagemagick image file manipulation *[http://tipsonubuntu.com/2016/11/02/install-ffmpeg-3-2-via-ppa-ubuntu-16-04/ How to install ffmpeg 3.2 in Ubuntu 16] === Downloading Youtube from shell === First install the Python [http://rg3.github.io/youtube-dl/download.html youtube-dl] tool, with '''pip''': <source lang="bash"> sudo pip install --upgrade youtube_dl </source> Then use the tool to download the video, e.g. <source lang="bash"> youtube-dl https://www.youtube.com/watch?v=f9m2yReECak </source> == System monitoring & management == List the top 10 memory consuming processes <source lang="bash"> ps -auxf | sort -nr -k 4 | head -10 </source> List the top 10 CPU consuming processes <source lang="bash"> ps -auxf | sort -nr -k 3 | head -10 </source> Limit CPU resources to a process (you may need to first install the '''cpulimit''' package): <source lang="bash"> cpulimit -b -l <PERCENTAGE> -p <PID> </source> == Network commands == === Restart the network after changing configuration === <source lang="bash"> /etc/init.d/networking restart </source> === List all the listening sockets and their ports and programs === <source lang="bash"> netstat -lp </source> === Get current default gateway === <source lang="bash"> netstat -nr </source> The default gateway is on the last line, it should have the U and G flags set === Release DHCP lease === <source lang="bash"> dhclient -r </source> === Obtain a new DHCP lease === <source lang="bash"> dhclient </source> === Scan a local subnet for active IP addresses === <source lang="bash"> sudo nmap -sP 192.168.1.0/24 </source> === Get the MAC address and hostname of an IP on the current subnet === <source lang="bash"> arp -a 192.168.1.1 </source> === Display traffic passing through a port === This is very useful for debugging interactions with services, for example the following command shows traffic going between a local ''elasticsearch'' service and a local client application. <source lang="bash"> sudo tcpdump port 9200 -qAi lo </source> === Make the system prefer IPv4 connections === Open '''/etc/gai.conf''' and uncomment the following line: <source> # # For sites which prefer IPv4 connections change the last line to # precedence ::ffff:0:0/96 100 </source> === Test which IPv6 address is being used for public connections === Servers can be assigned many IPv6 addresses, but which one should you assign to ''AAAA'' records pointing at the server? This command shows which address is being used to make outgoing connections which would be the best one to use for incoming connections as well. The address used to test the outgoing connection here is google's public DNS server. <source lang="bash"> ip r get to 2001:4860:4860::8888 </source> *'''See also:''' [https://bgp.he.net/ Assigned IPv6 address ranges] and [http://tldp.org/HOWTO/html_single/Linux+IPv6-HOWTO/ IPv6 HOWTO] == Internet == === Download an url to a local file with continuation === <source lang="bash"> curl -L -O -C - http://www.foo.bar/file </source> <source lang="bash"> wget -c http://www.foo.bar/file </source> === Download a copy of an entire site === This will download an entire site, if the site is already downloaded, then only newer files are transferred. <source> wget -m http://foo.bar </source> == Port forwarding == Port forwarding allows a remote client to gain access to a network so an intranet can be accessed. <source lang="bash"> ssh -fnNTL[PORT]:appserver:[PORT] username@sshdserver </source> Then point your webbrowsers proxy server to appserver:[PORT] and access the intranet etc. To subvert a firewalled environment where outgoing ssh is allowed. <source lang="bash"> $ ssh -D 9000 username@remotehost </source> Then point your web browser to a SOCKS proxy @ localhost:9000 Further it's possible to get ssh through a web proxy using [http://www.agroman.net/corkscrew/ corkscrew]. <source lang="bash"> ssh -oProxyCommand='corkscrew local_web_proxy proxy_port %h %p' username@remotehost </source> *[http://en.wikipedia.org/wiki/Port_forwarding Port_forwarding (Wikipedia)] *[http://www.securityfocus.com/infocus/1816 SSH Port Forwarding article] *[http://www.ssh.com/support/documentation/online/ssh/adminguide/32/Port_Forwarding.html Port Forwarding (ssh.com)] === Monitoring network traffic === You can get daily and monthly traffic statistics that are updated every five minutes by installing the ''vnstat'' package. This is very useful if your ISP enforces a traffic limit. You can get reports on individual network interfaces. Enable monitoring on a specific interface as follows: <source lang="bash"> vnstat --enable -i eth0 </source> And then you can get a report for an interface as follows: <source lang="bash"> vnstat -i eth0 </source> Example output: <source> monthly rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- Nov '17 82.43 MiB | 15.97 MiB | 98.40 MiB | 0.35 kbit/s ------------------------+-------------+-------------+--------------- estimated 91 MiB | 16 MiB | 107 MiB | daily rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- today 82.43 MiB | 15.97 MiB | 98.40 MiB | 10.67 kbit/s ------------------------+-------------+-------------+--------------- estimated 93 MiB | 17 MiB | 110 MiB | </source> == General == === Add and remove startup items === <source lang="bash"> update-rc.d ITEM defaults </source> <source lang="bash"> update-rc.d -f ITEM remove </source> === Date and time === Get the current (or another time specified in ''--date'') time in UNIX timestamp format: <source lang="bash"> date +%s date --date='01/30/2012 01:23:45' +%s </source> Convert a UNIX timestamp into a date/time in the current locale format: <source lang="bash"> date -d @1282368345 </source> == Specific guides == *[http://www.linuxstall.com/fstab/ All about fstab] *[https://www.networkworld.com/article/2693414/setting-limits-with-ulimit.html All about ulimit] *[http://www.folkstalk.com/2012/07/xargs-command-examples-in-unix-linux.html Using xargs] *[http://pubs.opengroup.org/onlinepubs/9699919799/utilities/date.html Date format codes] *[https://www.tecmint.com/customize-bash-colors-terminal-prompt-linux/ Setting shell colours] *[https://haydenjames.io/linux-networking-commands-scripts/ 59 networking commands and scripts] *[http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html Top Linux monitoring commands] == See also == *[http://files.fosswire.com/2007/08/fwunixref.pdf Linux commands cheat sheet] *[http://files.fosswire.com/2008/04/ubunturef.pdf Ubuntu commands cheat sheet] *[https://help.ubuntu.com/community/UsingTheTerminal Using The Terminal] ''- from Ubuntu help'' *[http://www.ee.surrey.ac.uk/Teaching/Unix/ Basic Linux Tutorial] *[https://debian-handbook.info/ The Debian Administrator's Handbook] *[http://www.cheatography.com/davechild/cheat-sheets/ Another excellent cheatsheet site] *[http://www.coker.com.au/bonnie++/ bonnie++] ''- easy to use disk benchmarking tool (good output explanation [http://www.jamescoyle.net/how-to/599-benchmark-disk-io-with-dd-and-bonnie here]) *[https://help.ubuntu.com/community/UbuntuBonding Bonding multiple network connections into one] ''- see also [http://www.linuxfoundation.org/collaborate/workgroups/networking/bonding#Frequently_Asked_Questions this] for more detail'' *[https://www.howtogeek.com/howto/30184/10-ways-to-generate-a-random-password-from-the-command-line/ 10 ways to make random passwords from the command line] *[http://www.terminalinflection.com/manual-grub-boot/ Manually booting from the GRUB prompt] *[https://www.digitalocean.com/community/tutorials/how-to-partition-and-format-storage-devices-in-linux Digital Ocean tutorial on formatting drives] *[https://www.2daygeek.com/efficient-ways-to-read-the-log-files-in-linux/ Efficient Ways To Read The Log Files In Linux] *[https://www.howtoforge.com/converting_rpm_to_deb_with_alien Convert an RPM to a DEB with alien] *[https://docs.01.org/clearlinux/latest/guides/maintenance/cpu-performance.html CPU power & performance adjustment] [[Category:Linux]][[Category:Help]]

Return to Linux commands.