Linux:Tools
From Cheatsheet
Common commands
# Scroll through a file with less less -s myfile.txt # Select line 5 from the output cat example.txt | sel -e '5' # Select lines from the output, starting from the top cat example.txt | head -5 # Select lines from the output, starting from the bottom cat example.txt | tail -5
Uncommon commands
# Crash the current server echo c > /proc/sysrq-trigger
Package managers
apt
# List package details and description apt show xxx # Show package description apt-cache search xxx # List installed packages apt list
rpm
# List all local RPM packages rpm -qa # Query for a specific installed rpm package rpm -qi nginx
ls
# List folders sorted by modified date
ls -trol
# List folder contents recursively
ls -alsR myfolder/
# List folder contents sorted by time, newest first and reverse order
ls -latr myfolder
# Print 9th column of folder contents
ll /mnt/btrfs/share1/ | awk '{print $9}'
tar
# Compress the destination directory and keep the source path within the zipped file tar -czvf name-of-archive.tar.gz /path/to/directory-or-file # Compress the destination directory, but put the folder contents into the . within the zipped file tar -czvf name-of-archive.tar.gz -C /path/to/directory-or-file . # Extract a tar.gz file to the current folder tar -xzvf name-of-archive.tar.gz
find
# Basic find command
find / -name name-to-search-for
# Search the current folder for all files
find . -name \*
# Search the current folder for all files and count them
find . -name \* | wc -l
# Search the current folder for all .log files and search & output any line containing string "error"
find . -name \*.log -exec grep -H error {} \;
# Search for all modified files between 2023-01-01 and 2023-12-30
find /var/log/ -type f -name "*" -newermt 2023-01-01 ! -newermt 2023-12-30
# Search for all modified folders between 2022-01-01 and 2022-02-10, limited to a single folders' depth
find -maxdepth 1 -type d -newermt 2022-01-01 ! -newermt 2022-02-10
# Screwing around
for i in $(find URL* -name "*.report" | sort); do echo "$i" && cat "$i" | grep TOTAL_SIZE ; done
for i in $(find URL* -name "*.report"); do basename "$i" | sort && cat "$i" | grep TOTAL_SIZE ; done
for i in $(find URL* -name "*.report"); do basename "$i" | sort && cat "$i" | grep TOTAL_SIZE | awk '{print $2}'; done
for i in $(find URL* -name "*.report"); do basename "$i" && cat "$i" | grep TOTAL_SIZE | awk '{print $2}'; done
for i in $(find * -name "*.report"); do basename "$i" && cat "$i" | grep TOTAL_SIZE | awk '{print $2}'; done
ll URL* | awk '{print $9}' | grep "*.report" | sort | for i in $(find * -name "*.report"); do basename "$i" && cat "$i" | grep TOTAL_SIZE | awk '{print $2}'; done
ll URL* | awk '{print $9}' | grep .report | sort | for i in $(find * -name "*.report"); do basename "$i" && cat "$i" | grep TOTAL_SIZE
find URL1 -name \*.report -exec grep -H TOTAL_SIZE {} \; | LC_ALL=C awk -M 'BEGIN{FS=OFS="\t"} {printf("%s\t%.02f\n", $1, $2/(1024*1024*1024))}' | sed -e 's~^.*/~~' -e 's~\..*SIZE~~' | sort
Less
25 = Go to line 25 G = Go to bottom of file / = Activate search mode /Error = Search for "Error" n = Move to next search result N = Move to previous search result
# Don't wrap long lines to the current screen (move left or right to see truncated line) less -S /var/log/syslog # Output a file's contents and read it with less cat /etc/snmpd/snmp.conf | less -S # Number the lines when viewing less -N /var/log/messages # Open less at the first search result. (Do not use space between the -p parameter and your search query) less -p"Error" /var/log/messages
SSH
# Execute 'ls' on a remote server and output the result to your shell session echo 'ls' | ssh -T user@10.0.20.75 # Execute a command on a remote server and output the result to a local file echo 'ls' | ssh -T user@10.0.20.75 > <filename>.log # Log in by providing a password in the CLI sshpass 'MyPassword' ssh -XY root@10.100.25.1
mdtest
This chapter was written and contributed by Ivo Palli.
General
mdtest is part of the ior performance test package.
Installation
wget https://github.com/hpc/ior/releases/download/3.3.0/ior-3.3.0.tar.bz2 tar xjf ior-*.tar.bz2 cd ior-*/ yum install openmpi-devel environment-modules # Relog your shell so 'module' is available module load mpi module list ./configure make -j4 make install
Usage
Note: Number of items should be a multiple of depth x branching factor
module load mpi mpirun --oversubscribe --allow-run-as-root -n 10 mdtest -n 2000 -z 5 -b 2 -d /mnt/nfs
