Linux tips
From silico.biotoul.fr
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= Paths & I/O & files = | = Paths & I/O & files = | ||
+ | |||
+ | == Linux filesystem organization == | ||
+ | |||
+ | {| style="border-collapse: separate; | ||
+ | border-spacing: 0; | ||
+ | border: 1px solid #000; | ||
+ | padding: 3px" | ||
+ | |- | ||
+ | | / || The root directory. | ||
+ | |} | ||
+ | * /boot This is where the Linux kernel and boot loader files are kept. The kernel is a file called vmlinuz. | ||
+ | /etc The /etc directory contains the configuration files for the system. All of the files in /etc should be text files. Points of interest: | ||
+ | |||
+ | /etc/passwd | ||
+ | The passwd file contains the essential information for each user. It is here that users are defined. | ||
+ | /etc/fstab | ||
+ | The fstab file contains a table of devices that get mounted when your system boots. This file defines your disk drives. | ||
+ | /etc/hosts | ||
+ | This file lists the network host names and IP addresses that are intrinsically known to the system. | ||
+ | /etc/init.d | ||
+ | This directory contains the scripts that start various system services typically at boot time. | ||
+ | |||
+ | /bin, /usr/bin These two directories contain most of the programs for the system. The /bin directory has the essential programs that the system requires to operate, while /usr/bin contains applications for the system's users. | ||
+ | /sbin, /usr/sbin The sbin directories contain programs for system administration, mostly for use by the superuser. | ||
+ | /usr The /usr directory contains a variety of things that support user applications. Some highlights: | ||
+ | |||
+ | /usr/share/X11 | ||
+ | Support files for the X Windows system | ||
+ | /usr/share/dict | ||
+ | Dictionaries for the spelling checker. Bet you didn't know that Linux had a spelling checker. See look and ispell. | ||
+ | /usr/share/doc | ||
+ | Various documentation files in a variety of formats. | ||
+ | /usr/share/man | ||
+ | The man pages are kept here. | ||
+ | /usr/src | ||
+ | Source code files. If you installed the kernel source code package, you will find the entire Linux kernel source code here. | ||
+ | |||
+ | /usr/local /usr/local and its subdirectories are used for the installation of software and other files for use on the local machine. What this really means is that software that is not part of the official distribution (which usually goes in /usr/bin) goes here. | ||
+ | |||
+ | When you find interesting programs to install on your system, they should be installed in one of the /usr/local directories. Most often, the directory of choice is /usr/local/bin. | ||
+ | /var The /var directory contains files that change as the system is running. This includes: | ||
+ | |||
+ | /var/log | ||
+ | Directory that contains log files. These are updated as the system runs. You should view the files in this directory from time to time, to monitor the health of your system. | ||
+ | /var/spool | ||
+ | This directory is used to hold files that are queued for some process, such as mail messages and print jobs. When a user's mail first arrives on the local system (assuming you have local mail), the messages are first stored in /var/spool/mail | ||
+ | |||
+ | /lib The shared libraries (similar to DLLs in that other operating system) are kept here. | ||
+ | /home /home is where users keep their personal work. In general, this is the only place users are allowed to write files. This keeps things nice and clean :-) | ||
+ | /root This is the superuser's home directory. | ||
+ | /tmp /tmp is a directory in which programs can write their temporary files. | ||
+ | /dev The /dev directory is a special directory, since it does not really contain files in the usual sense. Rather, it contains devices that are available to the system. In Linux (like Unix), devices are treated like files. You can read and write devices as though they were files. For example /dev/fd0 is the first floppy disk drive, /dev/sda (/dev/hda on older systems) is the first IDE hard drive. All the devices that the kernel understands are represented here. | ||
+ | /proc The /proc directory is also special. This directory does not contain files. In fact, this directory does not really exist at all. It is entirely virtual. The /proc directory contains little peep holes into the kernel itself. There are a group of numbered entries in this directory that correspond to all the processes running on the system. In addition, there are a number of named entries that permit access to the current configuration of the system. Many of these entries can be viewed. Try viewing /proc/cpuinfo. This entry will tell you what the kernel thinks of your CPU. | ||
+ | /media,/mnt Finally, we come to /media, a normal directory which is used in a special way. The /media directory is used for mount points. As we learned in the second lesson, the different physical storage devices (like hard disk drives) are attached to the file system tree in various places. This process of attaching a device to the tree is called mounting. For a device to be available, it must first be mounted. | ||
+ | |||
+ | When your system boots, it reads a list of mounting instructions in the file /etc/fstab, which describes which device is mounted at which mount point in the directory tree. This takes care of the hard drives, but you may also have devices that are considered temporary, such as CD-ROMs and floppy disks. Since these are removable, they do not stay mounted all the time. The /media directory is used by the automatic device mounting mechanisms found in modern desktop oriented Linux distributions. On systems that require manual mounting of removable devices, the /mnt directory provides a convenient place for mounting these temporary devices. You will often see the directories /mnt/floppy and /mnt/cdrom. To see what devices and mount points are used, type mount. | ||
+ | |||
== Paths & directories: <tt>pwd, mkdir, rmdir, rm</tt> == | == Paths & directories: <tt>pwd, mkdir, rmdir, rm</tt> == | ||
* <tt>pwd</tt> returns current directory | * <tt>pwd</tt> returns current directory |
Revision as of 13:15, 5 March 2013
Contents |
Paths & I/O & files
Linux filesystem organization
/ | The root directory. |
- /boot This is where the Linux kernel and boot loader files are kept. The kernel is a file called vmlinuz.
/etc The /etc directory contains the configuration files for the system. All of the files in /etc should be text files. Points of interest:
/etc/passwd
The passwd file contains the essential information for each user. It is here that users are defined.
/etc/fstab
The fstab file contains a table of devices that get mounted when your system boots. This file defines your disk drives.
/etc/hosts
This file lists the network host names and IP addresses that are intrinsically known to the system.
/etc/init.d
This directory contains the scripts that start various system services typically at boot time.
/bin, /usr/bin These two directories contain most of the programs for the system. The /bin directory has the essential programs that the system requires to operate, while /usr/bin contains applications for the system's users. /sbin, /usr/sbin The sbin directories contain programs for system administration, mostly for use by the superuser. /usr The /usr directory contains a variety of things that support user applications. Some highlights:
/usr/share/X11
Support files for the X Windows system
/usr/share/dict
Dictionaries for the spelling checker. Bet you didn't know that Linux had a spelling checker. See look and ispell.
/usr/share/doc
Various documentation files in a variety of formats.
/usr/share/man
The man pages are kept here.
/usr/src
Source code files. If you installed the kernel source code package, you will find the entire Linux kernel source code here.
/usr/local /usr/local and its subdirectories are used for the installation of software and other files for use on the local machine. What this really means is that software that is not part of the official distribution (which usually goes in /usr/bin) goes here.
When you find interesting programs to install on your system, they should be installed in one of the /usr/local directories. Most often, the directory of choice is /usr/local/bin. /var The /var directory contains files that change as the system is running. This includes:
/var/log
Directory that contains log files. These are updated as the system runs. You should view the files in this directory from time to time, to monitor the health of your system.
/var/spool
This directory is used to hold files that are queued for some process, such as mail messages and print jobs. When a user's mail first arrives on the local system (assuming you have local mail), the messages are first stored in /var/spool/mail
/lib The shared libraries (similar to DLLs in that other operating system) are kept here. /home /home is where users keep their personal work. In general, this is the only place users are allowed to write files. This keeps things nice and clean :-) /root This is the superuser's home directory. /tmp /tmp is a directory in which programs can write their temporary files. /dev The /dev directory is a special directory, since it does not really contain files in the usual sense. Rather, it contains devices that are available to the system. In Linux (like Unix), devices are treated like files. You can read and write devices as though they were files. For example /dev/fd0 is the first floppy disk drive, /dev/sda (/dev/hda on older systems) is the first IDE hard drive. All the devices that the kernel understands are represented here. /proc The /proc directory is also special. This directory does not contain files. In fact, this directory does not really exist at all. It is entirely virtual. The /proc directory contains little peep holes into the kernel itself. There are a group of numbered entries in this directory that correspond to all the processes running on the system. In addition, there are a number of named entries that permit access to the current configuration of the system. Many of these entries can be viewed. Try viewing /proc/cpuinfo. This entry will tell you what the kernel thinks of your CPU. /media,/mnt Finally, we come to /media, a normal directory which is used in a special way. The /media directory is used for mount points. As we learned in the second lesson, the different physical storage devices (like hard disk drives) are attached to the file system tree in various places. This process of attaching a device to the tree is called mounting. For a device to be available, it must first be mounted.
When your system boots, it reads a list of mounting instructions in the file /etc/fstab, which describes which device is mounted at which mount point in the directory tree. This takes care of the hard drives, but you may also have devices that are considered temporary, such as CD-ROMs and floppy disks. Since these are removable, they do not stay mounted all the time. The /media directory is used by the automatic device mounting mechanisms found in modern desktop oriented Linux distributions. On systems that require manual mounting of removable devices, the /mnt directory provides a convenient place for mounting these temporary devices. You will often see the directories /mnt/floppy and /mnt/cdrom. To see what devices and mount points are used, type mount.
Paths & directories: pwd, mkdir, rmdir, rm
- pwd returns current directory
- relative to current directory: e.g. ls subdir/subsubdir or ls ../whatever/
- absolute ls ~user/path or ls /home/user/path
- mkdir: create directory. e.g. mkdir ~/newdir or with subdirs mkdir -p ~/new/newsub/newsubsub
- rmdir dirname or if not empty rm -fr dirname
Permissions: chown, chgrp, chmod
$ ls -l /home drwxr-x--- 69 barriot gsi 4.0K Mar 5 12:09 barriot drwx------ 2 root root 16K Jul 12 2010 lost+found drwxr-xr-x 36 micas stage 4.0K Jul 31 2012 micas ... [barriot@gamborimbo ~]$ ls -lh Documents/TEACHING/2012-2013/M1-MABS/Graph/TP3-igraph.layout/ total 80K drwxr-xr-x 1 barriot gsi 4.0K Mar 14 2012 HDE.old -rw-r--r-- 1 barriot gsi 24K Mar 14 2012 91347.nwk -rw-r--r-- 1 barriot gsi 942 Mar 1 16:02 Cleandb_Luca_1_S_1_1_65_Iso_Tr_1-CC1.cod -rw-r--r-- 1 barriot gsi 28K Sep 7 2010 Cleandb_Luca_1_S_1_1_65_Iso_Tr_1-CC1.gr -rw-r--r-- 1 barriot gsi 2.3K Sep 7 2010 Cleandb_Luca_1_S_1_1_65_Iso_Tr_1-CC1.tgr -rw-r--r-- 1 barriot gsi 4.7K Mar 5 11:42 cmds.R -rw-r--r-- 1 barriot gsi 871 Mar 14 2012 sample_tree_with_branchlengths.nwk -rwxr-xr-x 1 barriot gsi 670 Mar 14 2012 drawTree.py -rw-r--r-- 1 barriot gsi 5.6K Feb 27 16:57 Tree.py
First character corresponds to file type. d for directory, - for a regular file, ... Then by 3 for the owner (user), the group and the others.
For a regular file :
- r for permission to read
- w for permission to modify
- x for being able to execute the file (binary executable or script)
For a directory :
- r to be able to read the content (list files in the directory)
- w to be able to add or remove files
- x to be able to pass through that directory, i.e. cd to that dir or a subdir
Modify ownership of a file or directory :
# change owner chown newuser file # recursive chown -R newuser directory # change group chgrp newgroup filename # change both chown newuser.newgroup filename
Modify permissions:
# numeric notation: r=4, w=2, x=1, thus for rwx-r-x--- chmod 760 file # recursively on a sub directory chmod -R 760 dirname # symbolic notation: chmod u=rwx,g=rx,o= filename # add execute permission for all: chmod a+x filename # revoke write permission for others: chmod o-w filename
File info & type: stat, file
[barriot@gamborimbo ~]$ stat /home/barriot File: `/home/barriot' Size: 12288 Blocks: 24 IO Block: 4096 directory Device: fd02h/64770d Inode: 1048577 Links: 119 Access: (0755/drwxr-xr-x) Uid: ( 500/ barriot) Gid: ( 501/ gsi) Access: 2013-03-05 10:39:08.927051453 +0100 Modify: 2013-03-05 10:39:00.240074369 +0100 Change: 2013-03-05 10:39:00.240074369 +0100 Birth: -
[barriot@gamborimbo ~]$ stat .bashrc File: `.bashrc' Size: 517 Blocks: 8 IO Block: 4096 regular file Device: fd02h/64770d Inode: 1052239 Links: 1 Access: (0755/-rwxr-xr-x) Uid: ( 500/ barriot) Gid: ( 501/ gsi) Access: 2013-03-02 16:04:19.268619379 +0100 Modify: 2012-10-12 17:24:24.818899216 +0200 Change: 2012-11-18 23:25:18.869870338 +0100 Birth: -
[barriot@gamborimbo ~]$ file /home/barriot /home/barriot: directory
[barriot@gamborimbo ~]$ file .bashrc .bashrc: ASCII text
File content, concatenation, split, ... and redirections: cat, split, head, tail, more, less, tac
# display content cat somefile.txt # concatenate 2 or more files cat file_1.txt file_2.txt cat *.txt # redirect to a file (if file exists it will be overwritten otherwise it gets created) cat file_1.txt file_2.txt > result.txt # redirect to a file (if file exists it will be appended at the end otherwise it gets created) cat others*.txt >> result.txt # split a file into smaller parts ## by file size (1kb) split --bytes 1024 big.file split -b 1024 big.file ## by number of lines per output files split --lines 100 big.text.file.txt split -l 100 big.text.file.txt ## by number of output files split --number 10 big.file split -n 10 big.file ## specify output files prefix and numbered numerically (3 digits) split -n 100 -a 3 -d big.file part_ split -n 100 --suffix-length 3 --numeric-suffixes big.file part_
redirection, head, tail, more, less, tac, sed, grep, cut, find, wc, sort
Processes
ps, jobs, Ctrl-C/Z/D, top, kill, killall, nohup, disown, &
shell
variables, test, $?, for, if, function, $(cmd), && ||
archive
tar, bzip, gzip, rsync