UNIX commands
The following are some basic commands which may be useful in the UNIX/Linux Shell
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Working with directories
Note that you can always discover what directory you are currently in using the pwd command:
[server]$ pwd /home/current/directory/ [server]$
Creating directories
To create a new directory, use the mkdir command:
[server]$ mkdir directory_name [server]$
Deleting directories
There are actually a few ways to delete directories in the shell. To delete an empty directory, use the rmdir command:
[server]$ rmdir directory_name [server]$
To delete a non-empty directory (one that still contains files or other directories in it) rmdir will not work. Here you have two choices. You can either remove all the contained files and directories by hand using the rmdir and rm commands, or you can use rm's -r flag.
[server]$ rm -r directory_name [server]$
Be careful using this flag, as you will delete everything contained in the directory specified. There is no "Recycle Bin" or "Trash Can" in the shell. What you delete is gone forever, so use caution.
Changing directories
To change to another directory, use the cd command:
[server]$ cd /target/directory [server]$
A successful change will not return any messages.
To change to your previous directory, use the cd - command:
[server]$ pwd /current/directory/ [server]$ cd /new/directory/ [server]$ pwd /new/directory/ [server]$ cd - [server]$ pwd /current/directory/ [server]$
The user above has changed from one directory to another, then used the cd - command to return to their previous directory.
You can go to the parent directory quickly by using the ../.
cd ../
You can go up multiple directories by stringing the ../ together.
cd ../../
List contents of current directory
To list the contents of a directory, use the ls command:
[server]$ ls Maildir example.com logs [server]$
Add the -l flag to list the contents with full details, including permissions, file size and last modified date:
[server]$ ls -l drwx--S--- 12 username groupname 4096 Mar 15 17:28 Maildir drwxr-xr-x 5 username groupname 4096 Mar 7 12:35 example.com drwxr-sr-x 8 root root 4096 Apr 17 06:33 logs [server]$
To list all files within the directory including hidden files add the -a flag:
[server]$ ls -a . .bash_profile example.com .. .bashrc logs .bash_history Maildir [server]$
ls sorting
Some of you might notice that the ls settings show up in a semi-alphabetical order with dot files (files starting with dots) and cased files intermixed. Like so:
[server]$ ls -a . .bash_profile example.com TEMP .. .bashrc .gnome .vimrc .bash_history Maildir logs [server]$
This has to do with the $LANG setting allowing ls to sort based on your local language. To fix this and put it back to "normal" ls listing, unset your $LANG environment variable.
[server]$ unset LANG [server]$ ls -a . .bash_profile .vimrc example.com .. .bashrc Maildir logs .bash_history .gnome TEMP [server]$
You can add the unset command into your .bashrc file (at the end) so that it unsets everytime you log into the server.
Directory sizes
To determine the size of a directory, use the du command:
[server]$ du example.com 1532 example.com [server]$
Add the -sh flag for more human readable format. You can also list multiple directories and files seperated by spaces.
Working with files
Creating files
To create a new file, you can either save it from within a text editor or other program, or you can use the touch command:
[server]$ touch filename [server]$
This creates an empty file named filename.
Moving files
To move a file to another place:
[server]$ mv /old/location/filename /new/location/filename [server]$
Note that you can also use relative paths:
[server]$ mv filename ../directory/filename [server]$
Copying files
To copy a file to another place:
[server]$ cp /existing/location/filename /new/location/filename [server]$
Renaming files
mv is also used to rename a file to something else:
[server]$ mv oldfilename newfilename [server]$
Delete files
To delete a file:
[server]$ rm filename [server]$
You can use wildcards to delete multiple files with similar names. To delete all files beginning with "pic" (eg, pic01.jpg, pic02.jpg, etc):
[server]$ rm pic* [server]$
The wildcard can appear anywhere in the string. To delete all .jpg files:
[server]$ rm *.jpg [server]$
Be careful when using wildcards - you can inadvertently delete files this way. Using the -i flag, you will be asked to confirm deleting files. Type y or n as prompted:
[server]$ rm -i *.jpg rm: remove 'example1.jpg'? y rm: remove 'example2.jpg'? y [server]$
Locating files
To locate all of the files in a directory tree that contain some pattern in their name:
[server]$ find directory -name <regexp> -print list of results [server]$
Note that this command uses a regular expression (<regexp> above) to describe the filename. You can also type in the exact filename.
For example, to find all files ending with htm in the current directory and any subdirectories:
[server]$ find . -name *.htm -print
Note that searches containing wildcards ("*", ".","?") should be bounded by quotes so that the shell does not try to interpret them as regular expressions:
[server]$ find . -name "*.htm" -print
Further, -print is the default on most Unix/Linux systems so it can be omitted in most instances:
[server]$ find . -name "*.htm"
The find command is extremely powerful. One other handy use is to delete all of the empty subfolders in a particular tree. For example:
[server]$ find . -depth -type d -empty -exec rmdir {} ';'
Just make sure you don't leave off the -empty!
This command will search in the current directory and all sub directories. All files that contain the string will have their path printed to standard output:
[server]$ find . -exec grep "some_string" '{}' \; -print
To find all the files that have been modified in the last 7 days and output them to a file:
[server]$ find . -mtime -7 > mod.txt
Disk usage
The panel doesn't show disk usage for dedicated servers. You'll just need to SSH/telnet to your server and use df. This will show you total, used, and available disk space. Adding the -h flag displays the numbers in an easier to read format.
[server]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda1 2.0G 1.1G 876M 55% /
/dev/hda3 4.9G 2.7G 1.9G 58% /usr/local
10.3.19.71:/vol/pulpy/postal/babricus
239G 220G 19G 92% /home/.babricus
10.3.19.114:/vol/chippy/postal/abubu
239G 211G 28G 89% /home/.abubu
10.3.19.112:/vol/wetty/postal/cabernet
191G 169G 22G 89% /home/.cabernet...
[server]$
Note that the output above was truncated. The actual output on DreamHost's servers can be quite a bit longer.
Your home directory and all your files are in /home (not listed above).
In the example below, the home directory is listed, and you can see from this that 26% percent of a 30GB partition is being used.
[server] df -h Filesystem 1k-blocks Used Available Use% Mounted on /dev/hda1 2071416 1017516 948676 52% / /dev/hda3 5162828 1036076 3864492 22% /usr/local /dev/hda4 30273148 7413324 21322004 26% /home /dev/hdd1 78786704 6505004 68279540 9% /mnt/backup
If you're just interested in knowing how much space a directory and its contents are taking up, you can use this command instead:
[server]$ du -sh directory_name 52M directory_name
Users
To get login details:
last <username>
External links
Unix tutorials
- Learn UNIX in 10 Minutes Note: Not everything mentioned here can be used at Dreamhost.
- UNIX Tools - Power Point Presentation Note: CPT247 College Course.
- Unix Administration - Power Point Presentation Note: CPT248 College Course.
