Command Line Utilities: Difference between revisions
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* This is the command used on Gentoo to change an user's groups. You can also edit /etc/group, but this is not the right way of doing things. It will usually fail because you also need to change /etc/gshadow. Note that /etc/group- is just a backup of /etc/group. | * This is the command used on Gentoo to change an user's groups. You can also edit /etc/group, but this is not the right way of doing things. It will usually fail because you also need to change /etc/gshadow. Note that /etc/group- is just a backup of /etc/group. | ||
== useradd == | |||
* Command to add a new user. | |||
= Other = | = Other = | ||
Revision as of 15:37, 17 August 2009
This is a collection of random useful command line tools.
Network Related
rsync
- --no-p: this will disable permissions synchronization.
- --no-o: this will disable owner synchronization.
nmap
- This program allows you to test if a port is open on a remote box.
netstat
- netstat -altp will list all the open ports on your machine, along with the process that opened it. Very useful!
File & I/O
- To obtain the space available on a HD: df -h
- To obtain a list of the sizes of all the directories of the current directory: du --max-depth=1 -h
tar
- Use the -C option to switch to a directory before compressing. Very useful.
- Use the -h option to follow symbolic links.
cpio
- This seems to be something similar to tar.
- Allows you to do nice stuff like
find . -name '*.txt' print0 | cpio -o -0 | ssh elvanor@otherbox 'cd dirB && cpio -iduv -0'
This would copy the *.txt files to another box, preserving the directory hierarchy.
Administration
gpasswd
- This is the command used on Gentoo to change an user's groups. You can also edit /etc/group, but this is not the right way of doing things. It will usually fail because you also need to change /etc/gshadow. Note that /etc/group- is just a backup of /etc/group.
useradd
- Command to add a new user.
Other
ps
- The legend for the status letters of processes can be found in the man page. R basically means running, and S means sleeping.
- Something very tricky can happen with ps: ps lists a process, but ps | grep will not. This is because if processes are always spawned and short lived (which means you have a problem on your system), ps when started on a shell will get the time to catch the process but ps | grep will run faster (less text to output) and so won't catch the process. A way to check for signs of this problem is to launch htop and see if the CPU is at 100% usage.
- ps can display the environment of the current running processes, with the e option.
Tricks and tips
- Redirecting all outputs to a file:
foo &> bar
To redirect only stderr:
foo 2> bar