In this article, let us review the Linux filesystem structures and understand the meaning of individual high-level directories.
/ – Root
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Every single file and directory starts from the root directory.
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Only root user has write privilege under this directory.
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Please note that /root is root user’s home directory, which is not same as /.
/bin – User Binaries
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Contains binary executables.
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Common linux commands you need to use in single-user modes are located under this directory.
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Commands used by all the users of the system are located here.
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For example: ps, ls, ping, grep, cp.
/sbin – System Binaries
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Just like /bin, /sbin also contains binary executables.
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But, the linux commands located under this directory are used typically by system aministrator, for system maintenance purpose.
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For example: iptables, reboot, fdisk, ifconfig, swapon
/etc – Configuration Files
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Contains configuration files required by all programs.
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This also contains startup and shutdown shell scripts used to start/stop individual programs.
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For example: /etc/resolv.conf, /etc/logrotate.conf
/dev – Device Files
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Contains device files.
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These include terminal devices, usb, or any device attached to the system.
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For example: /dev/tty1, /dev/usbmon0
/proc – Process Information
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Contains information about system process.
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This is a pseudo filesystem contains information about running process. For example: /proc/{pid} directory contains information about the process with that particular pid.
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This is a virtual filesystem with text information about system resources. For example: /proc/uptime
/var – Variable Files
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var stands for variable files.
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Content of the files that are expected to grow can be found under this directory.
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This includes — system log files (/var/log); packages and database files (/var/lib); emails (/var/mail); print queues (/var/spool); lock files (/var/lock); temp files needed across reboots (/var/tmp);
/tmp – Temporary Files
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Directory that contains temporary files created by system and users.
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Files under this directory are deleted when system is rebooted.
/usr – User Programs
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Contains binaries, libraries, documentation, and source-code for second level programs.
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/usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look under /usr/bin. For example: at, awk, cc, less, scp
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/usr/sbin contains binary files for system administrators. If you can’t find a system binary under /sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel
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/usr/lib contains libraries for /usr/bin and /usr/sbin
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/usr/local contains users programs that you install from source. For example, when you install apache from source, it goes under /usr/local/apache2
/home – Home Directories
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Home directories for all users to store their personal files.
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For example: /home/john, /home/nikita
/boot – Boot Loader Files
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Contains boot loader related files.
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Kernel initrd, vmlinux, grub files are located under /boot
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For example: initrd.img-2.6.32-24-generic, vmlinuz-2.6.32-24-generic
/lib – System Libraries
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Contains library files that supports the binaries located under /bin and /sbin
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Library filenames are either ld* or lib*.so.*
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For example: ld-2.11.1.so, libncurses.so.5.7
/opt – Optional add-on Applications
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opt stands for optional.
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Contains add-on applications from individual vendors.
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add-on applications should be installed under either /opt/ or /opt/ sub-directory.
/mnt – Mount Directory
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Temporary mount directory where sysadmins can mount filesystems.
/media – Removable Media Devices
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Temporary mount directory for removable devices.
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For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD writer
/srv – Service Data
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srv stands for service.
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Contains server specific services related data.
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For example, /srv/cvs contains CVS related data.