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Cover image for Linux commands for sysadmins (but not only, part 1)

Linux commands for sysadmins (but not only, part 1)

dandyvica profile image Alain Viguier 惻2 min read

Whether you're a Linux or an OS/X user, you often ends up starting a terminal and typing some shell commands.

Following is a list of some commands I often use, and they're by no means exhaustive. They are given as examples, and a second list will include other topics like benchmarking, network, or performance. Some require the root password or at least be part of the sudoers.

Be warned these are mainly Linux commands, used from a Linux Mint 19.3 machine. My advice is to man each one (when available) to list all the numerous possibilities for a specific command. man is always your friend and you can often discover the missing parameter you need to solve your problem.

Dealing with hardware

  • list your hardware configuration (the most comprehensive): inxi -Fxz

  • disks

what? command
list all hard disks lsblk -o NAME,TYPE,SIZE,MODEL,SERIAL,VENDOR -d
get information on a disk sudo hdparm -i /dev/sda
list partitions sudo sfdisk -l /dev/sda
mounted disks df -T -x squashfs -x tmpfs -x devtmpfs
sanitize or partition dcfldd if=/dev/urandom od=/dev/sdX
copy a disk or partition to a file image dcfldd if=/dev/sdX of=image.img hash=sha1 conv=sync,noerror
list usb devices lsusb
list PCI devices lspci

Files

Listing files with ls

list command
sort by size (largest first) ls -lS
sort by time (newest first) ls -lt
reverse sorting order add the -r flag
recursive ls -lR
sort by extension ls -lX

Using the tree command

If not installed: sudo apt-get install tree

list command
only directories tree -d
full path with files tree /usr -f
on the current filesystem only tree . -x
only subdirectories tree . -L 1
only files with pattern tree . -P ".jpg"*
without indentation (like find) tree . -i -f
output as a JSON object tree . -J
output as an XML object tree . -X

Finding files

find is a very feature rich command and not easy to master at first. man find is your friend!

find command
files matching a pattern find . -name '.jpg'*
files matching a pattern (case insensitive) find . -iname '.jpg'*
files only on current mounted filesystems find . -mount -name ".jpg"*
owned by userID find . -user 1000
whose permissions are 644 find . -perm 644
greater than 50M find / -size +50M
modified more than 1 day find . -mtime +1
only directories find . -type d
only (regular) files find . -type f
executable files find . -executable -type f
using a regex find . -regextype posix-extended -regex "(..jpg

Open files

lsof is a very powerful and versatile command.

find command
open files for a list of users lsof -u johndoe,1000
open files by a list of processes lsof -p 1999,2050
on a specific fiessystem lsof /dev/sdb1

Photo by Barn Images on Unsplash

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dandyvica profile

Alain Viguier

@dandyvica

Senior software engineer & sysadmin, technical architect, Linux expert. Always willing to learn new stuff.

Discussion

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I'd have started with saying that the man command is your friend, because it provides you with the manual pages for each of these commands. It's meta-powerful :-)

 

Great and concise summary!
I would add find -delete option in the list.
Also for disk usage I discovered ncdu which a nice command line tool.