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ps
Options
-e show all proccesses
-f full description
-F extra full
-u user list only processes belonging to user
–forest lists processes as a tree structure
-T show the threads with SPID
-L show the threads with LWP/NLWP columns
-C list by command name
r restricts to only running processes
e shows the environment after the command
Process state codes
D Uninterruptible sleep (usually IO)
R Running or runnable (on run queue)
S Interruptible sleep (waiting for an event to complete)
T Stopped, either by a job control signal or because it is being traced.
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z Defunct (“zombie”) process, terminated but not reaped by its parent
Example:
ps -Lu mysql -o tid,state,%cpu,%mem,etime,nlwp,comm,sgi_p
The above lists all mysql threads with these columns: thread id, state of the process (short description; for long use stat), cpu percentage usage (per thread), memory percentage usage (shared), elapsed time, number of lightweight processes (threads), name of the command and the number of the used CPU / core with * if the process is sleeping.
yum
Repositories
The DAG repository ATrpms repository RPMforge repository FreshRPMS repository Dries repository
Relevant paths
/etc/yum.conf
/etc/yum.repos.d
Installs a package
yum install package
Checks for updates
yum chech-update [pack]
Updates a package
yum update package
Information
yum info package
Listing packages
yum list [all]
yum list [regexp]
yum list available [regexp]
yum list updates [regexp]
yum list installed [regexp]
yum list obsoletes [regexp]
Cleaning
yum clean packages (erases the downloaded packages)
yum clean headers (cleans the syncing headers)
yum clean all
Erases package
yum erase package
Searches for a package after a word
yum search keyword
Options
-y to assume yes to all confirmation questions (for scripting automation)
rpm
Installs the pack verbosely and printing 50 hash marks
rpm -ivh pack
Forces a pack install even if the dependencies are not met
–force
Searches all the installed packages
rpm -qa
Searches to what package a file belongs
rpm -f file
Queries all files that belong to a pack
rmp -ql pack
Queries documentation for a package
rpm -qd pack
Queries all the dependencies
rpm -qR pack
Updates an existing package
rpm -F pack
Updates pack if it exists or installs it if it doens’t exist
rpm -U pack
Erases a package
rpm -e pack
Rebuilds the RPM database if it becomes corrupt
rpm –rebuilddb
exim commands
Show the mail queue
exim -bp
Process the mail queue (non force)
exim -q
Process the mail queue forcing delivery except for the frozen messages
exim -qf
Process the mail queue forcing even the frozen messages into delivery
exim -qff
Stat the mail queue
exim -bp | exiqsumm
Print out what exim is doing right now
exiwhat
Count the mail messages in the queue
exim -bpc
For further research
exiqgrep -o 86400 -i | xargs exim -MrmThe above command will delete the messages older than 1 day. To delete email more than one day you can multiply with the number of days with 86400.
Further reference: http://bradthemad.org/tech/notes/exim_cheatsheet.php
diff
Lists differences between 2 files
-i case insensitive
-y list on columns
-w ignores whites (spaces)
-B ignores spaces
-c full compare
file
Lists the file type
file file_in_question
Lists the file type without changing the atime
file -p file_in_question
stat
Lists size, owner, group, device, inode, file type, file perms, atime, ctime, mtime about file
stat file
wc
Counts the lines from a file
wc -l file
Counts the words from a file
wc -w file
Counts the chars from a file
wc -m file