Difference between revisions of "Fstab"
(→Resources: rm'ed ubuntu forum post link, this wiki page covers everything)
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/dev/sdg1 /media/backup jfs defaults,nofail 0 2
/dev/sdg1 /media/backup jfs defaults,nofail 0 2
== Related ==
* [[Persistent block device naming]]
*[[Persistent block device naming]]
* [[Writing on a FAT32 partition as a normal user]]
*[[Writing on a FAT32 partition as a normal user]]
* [[NTFS Write Support]]
*[[NTFS Write Support]]
* [[Using tmpfs for /var/*]]
*[[Using tmpfs for /var/*]]
== Resources ==
== Resources ==
Revision as of 06:09, 17 May 2011
The Template:Filename file contains static filesystem information. It defines how storage devices and partitions are to be initialized and integrated into the overall system.
Here is an example Template:Filename using kernel naming (/dev/sdx) descriptors:
# <file system> <dir> <type> <options> <dump> <pass> devpts /dev/pts devpts defaults 0 0 shm /dev/shm tmpfs nodev,nosuid 0 0 /dev/sda2 / ext4 defaults,noatime 0 1 /dev/sda6 /home ext4 defaults,noatime 0 2 /dev/sda7 swap swap defaults 0 0
Here is another example using more mount options and the LABEL= method of identifying mountable devices.
devpts /dev/pts devpts defaults 0 0 shm /dev/shm tmpfs nodev,nosuid 0 0 LABEL=BOOT /boot ext2 defaults 0 2 LABEL=ROOT / ext4 defaults,noatime 0 1 LABEL=USR /usr ext4 defaults,noatime 0 2 LABEL=VAR /var ext4 defaults,noatime 0 2 LABEL=OPT /opt ext4 defaults,noatime 0 2 LABEL=HOME /home ext4 defaults,noatime 0 2
Template:Filename contains the following fields separated by a space or tab:
<file system> <dir> <type> <options> <dump> <pass>
- <file systems> - defines the storage device (i.e. Template:Filename).
- <dir> - tells the mount command where it should mount the <file system> to.
- <type> - defines the file system type of the device or partition to be mounted. Many different file systems are supported. Some examples are: ext2, ext3, reiserfs, xfs, jfs, smbfs, iso9660, vfat, ntfs, swap, and auto. The 'auto' type lets the mount command to attempt to guess what type of file system is used, this is useful for removable devices such as cdroms and dvds.
- <options> - define particular options for filesystems. Some options relate only to the filesystem itself. Some of the more common options are:
- auto - File system will mount automatically at boot, or when the command 'mount -a' is issued.
- noauto - The filesystem is mounted only when you tell it to.
- exec - Allow the execution binaries that are on that partition (default).
- noexec - Do not allow binaries to be executed on the filesystem.
- ro - Mount the filesystem read only
- rw - Mount the filesystem read-write
- sync - I/O should be done synchronously
- async - I/O should be done asynchronously
- flush - specific option for FAT to flush data more often, thus making copy dialogs or progress bars to stays up until things are on the disk
- user - Permit any user to mount the filesystem (implies noexec,nosuid,nodev unless overridden.)
- nouser - Only allow root to mount the filesystem. (default)
- defaults - Default mount settings (equivalent to rw,suid,dev,exec,auto,nouser,async).
- suid - Allow the operation of suid, and sgid bits. They are mostly used to allow users on a computer system to execute binary executables with temporarily elevated privileges in order to perform a specific task.
- nosuid - Block the operation of suid, and sgid bits.
- noatime - Do not update inode access times on the filesystem. Can help performance (see atime options).
- nodiratime - Do not update directory inode access times on the filesystem. Can help performance (see atime options).
- relatime - Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than the current modify or change time. (Similar to noatime, but doesn't break mutt or other applications that need to know if a file has been read since the last time it was modified.) Can help performance (see atime options).
- <dump> - Is used by the dump utility to decide when to make a backup. When installed (not installed by a standard installation of Arch Linux), dump checks the entry and uses the number to decide if a file system should be backed up. Possible entries are 0 and 1. If 0, dump will ignore the file system, if 1, dump will make a backup. Most users will not have dump installed, so they should put 0 for the <dump> entry.
- <pass> fsck reads the <pass> number and determines in which order the file systems should be checked. Possible entries are 0, 1, and 2. The root file system should have the highest priority, 1, all other file systems you want to have checked should get a 2. File systems with a <pass> value 0 will not be checked by the fsck utility.
You can define the filesystems in the Template:Filename configuration in three different ways: by kernel naming descriptors, by UUID, or by labels. The advantage of using UUIDs or labels is that they are not dependent on disk order. This is useful if you change your storage device order in the BIOS, you switch storage device cabling, or because some BIOS's may occasionally change the order of storage devices.
You can get kernel naming descriptors using Template:Codeline:
# fdisk -l ... Device Boot Start End Blocks Id System /dev/sda1 * 1 2550 20482843+ b W95 FAT32 /dev/sda2 2551 5100 20482875 83 Linux /dev/sda3 5101 7650 20482875 83 Linux /dev/sda4 7651 121601 915311407+ 5 Extended /dev/sda5 7651 10200 20482843+ 83 Linux /dev/sda6 10201 17849 61440561 83 Linux /dev/sda7 17850 18104 2048256 82 Linux swap / Solaris /dev/sda8 18105 18113 72261 83 Linux /dev/sda9 18114 121601 831267328+ 7 HPFS/NTFS
# blkid /dev/sda1: UUID="76E4F702E4F6C401" LABEL="vista" TYPE="ntfs" /dev/sda2: LABEL="Root" UUID="24f28fc6-717e-4bcd-a5f7-32b959024e26" TYPE="ext4" /dev/sda6: LABEL="Home" UUID="03ec5dd3-45c0-4f95-a363-61ff321a09ff" TYPE="ext4" /dev/sda7: LABEL="swap" UUID="4209c845-f495-4c43-8a03-5363dd433153" TYPE="swap" /dev/sda10: UUID="0ea7a93f-537c-4868-9201-0dc090c050e4" TYPE="crypto_LUKS" /dev/mapper/sda10: UUID="d3560bbb-b5d5-46c5-a7a8-434c885217c7" UUID_SUB="425ab275-d520-4636-8d16-55fb2b957971" TYPE="btrfs"
An example Template:Filename using the UUID identifiers:
# <file system> <dir> <type> <options> <dump> <pass> none /dev/pts devpts defaults 0 0 none /dev/shm tmpfs defaults 0 0 UUID=24f28fc6-717e-4bcd-a5f7-32b959024e26 / ext4 defaults,noatime 0 1 UUID=03ec5dd3-45c0-4f95-a363-61ff321a09ff /home ext4 defaults,noatime 0 2 UUID=4209c845-f495-4c43-8a03-5363dd433153 swap swap defaults 0 0
The device or partition is required to be labeled first. To do this, you can use common applications like Template:Package Official to label partitions or you can use Template:Codeline to label ext2, ext3, and ext4 partitions. Keep in mind that not all file system have labeling support (e.g. FAT file systems).
A device or partition must not be mounted before attempting to label them. Initially you will need to boot from a Live(CD/DVD/USB) before you can label with a Template:Package Official-like application or for ext partitions you can use Template:Codeline.
e2label /dev/<disk-or-partition> Arch_Linux
Labels can be up to 16 characters long. Technically labeling can have spaces too, however there is no way to have your Template:Filename or GRUB configuration file (for that matter) be able to recognize them by that label if you do.
Labels should be unambiguous, meaning that each label should be original to prevent any possible conflicts. To enter labels into your Template:Filename, here is an example:
# <file system> <dir> <type> <options> <dump> <pass> devpts /dev/pts devpts defaults 0 0 shm /dev/shm tmpfs nodev,nosuid 0 0 LABEL=Arch_Linux / ext4 defaults,noatime 0 1 LABEL=Arch_Swap swap swap defaults 0 0
The use of Template:Codeline, Template:Codeline or Template:Codeline can help disk performance for ext2, ext3, and ext4 filesystems. Linux by default keeps a record (writes to the disk) every times it reads from the disk Template:Codeline. This was more purposeful when Linux was being used for servers; it doesn't have much value for desktop use. The worst thing about the default Template:Codeline option is that even reading a file from the page cache (reading from memory instead of the disk) will still result in a disk write! Using the Template:Codeline option fully disables writing file access times to the disk every time you read a file. This works well for almost all applications, except for a rare few like Mutt that need the such information. For mutt, you should only use the Template:Codeline option. Using the Template:Codeline option enables the writing of file access times only when the file is being modified (unlike Template:Codeline where the file access time will never be changed and will be older than the modification time). The Template:Codeline option disables the writing of file access times only for directories while other files still get access times written. The best compromise might be the use of Template:Codeline in which case programs like Mutt will continue to work, but you'll still have a performance boost because files will not get access times updated unless they are modified.
tmpfs is a temporary filesystem that resides in memory and/or your swap partition(s), depending on how much you fill it up etc. This may be a good way of speeding up some parts of the system, and to automatically clear some files on reboot.
By default, a tmpfs partition is set to half your total ram, but this can be customized. Note that the actual memory/swap consumption depends on how much you fill it up, tmpfs partitions don't claim any memory before it's actually used.
To use tmpfs for /tmp add this line to /etc/fstab:
tmpfs /tmp tmpfs defaults,nodev,nosuid,mode=1777 0 0
You may or may not want to specify the size here, but you should leave the mode part alone in these cases, to make sure that they have the correct permissions. In the above example, /tmp will be set to half your total ram, and the other 2 will be set to 10 mb each.
See the mount command man page for more information.
Reboot for the changes to come into effect. Note that while it may be tempting and sometimes useful, you should NOT just run mount -a, since this will make any current content in those locations inaccessible (you may want to keep active lockfiles for example). However, if all of them are empty, it should be safe to run mount -a instead of rebooting. You could also run mount /tmp etc to activate some now and the rest after reboot.
After applying changes, you way want to verify that it's working with df (df -h in this case):
tmpfs 2.0G 20K 2.0G 1% /tmp
To use tmpfs for /var/run and /var/run, you can simply symlink them to /run. Make sure to close anything important before doing this, because you'll have to reboot and daemons may not stop cleanly.
Dealing with paths that contain spaces
You can use the escape character followed by the 3 digit octal code for space "\040".
/dev/sda7 /home/username/Camera\040Picures ext4 defaults,noatime 0 2 UUID=7D4500B3071E18B2 /media/100\040GB\040(Storage) ntfs defaults,noatime,user 0 0
External drives that are to be mounted when present but ignored if absent may require the Template:Codeline option. This prevents errors being reported at boot.
/dev/sdg1 /media/backup jfs defaults,nofail 0 2
- Persistent block device naming
- Writing on a FAT32 partition as a normal user
- NTFS Write Support
- Firefox Ramdisk
- Using tmpfs for /var/*