{"id":3129,"date":"2014-06-12T22:43:06","date_gmt":"2014-06-12T14:43:06","guid":{"rendered":"http:\/\/rmohan.com\/?p=3129"},"modified":"2014-06-12T22:43:06","modified_gmt":"2014-06-12T14:43:06","slug":"e2label-fdisk-etcfstab-mount-linux-rescue-rescue-disk-centos","status":"publish","type":"post","link":"https:\/\/mohan.sg\/?p=3129","title":{"rendered":"e2label, fdisk, \/etc\/fstab, mount, linux rescue, rescue disk, CentOS"},"content":{"rendered":"\n\n\n\n
Tutorial: e2label, fdisk, \/etc\/fstab, mount, linux rescue, rescue disk, CentOS<\/b><\/td>\n<\/tr>\n
\nLet’s run through an example of a fresh disk, that needs to be configured, going through partitioning with fdisk, make filesystem, filesystem labelled using e2label, \/etc\/fstab edited, and mounted using mount. This is relevent for CentOS 3.x, 4.x 5.x; YMMV for other flavours.<\/p>\n

First, a run through of each command, with usage examples.<\/p>\n

fdisk<\/b><\/span><\/p>\n

if the partitioning of the drive is unknown, fdisk -l can be used to list the partition table of the drive. eg. fdisk -l \/dev\/sdb<\/p>\n

following is an example of a disk without a partition table<\/p>\n

# fdisk -l \/dev\/sdb<\/p>\n

Disk \/dev\/sdb: 74.3 GB, 74355769344 bytes
\n255 heads, 63 sectors\/track, 9039 cylinders
\nUnits = cylinders of 16065 * 512 = 8225280 bytes<\/p>\n

Disk \/dev\/sdb doesn’t contain a valid partition table<\/p>\n

and here’s an example of a disk with valid partition table<\/p>\n

# fdisk -l \/dev\/sda<\/p>\n

Disk \/dev\/sda: 299.9 GB, 299974524928 bytes
\n255 heads, 63 sectors\/track, 36469 cylinders
\nUnits = cylinders of 16065 * 512 = 8225280 bytes<\/p>\n\n\n\n\n\n\n
Device<\/b><\/td>\nBoot<\/b><\/td>\nStart<\/b><\/td>\nEnd<\/b><\/td>\nBlocks<\/b><\/td>\nId<\/b><\/td>\nSystem<\/b><\/td>\n<\/tr>\n
\/dev\/sda1<\/td>\n*<\/td>\n1<\/td>\n13<\/td>\n104391<\/td>\n83<\/td>\nLinux<\/td>\n<\/tr>\n
\/dev\/sda2<\/td>\n<\/td>\n14<\/td>\n268<\/td>\n2048287+<\/td>\n82<\/td>\nLinux swap<\/td>\n<\/tr>\n
\/dev\/sda3<\/td>\n<\/td>\n269<\/td>\n36469<\/td>\n290784532+<\/td>\n83<\/td>\nLinux<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

to change the partitions on a drive without partition table, such as a new drive, use fdisk\u00a0<\/span>
\neg. fdisk \/dev\/sdb<\/p>\n

# fdisk \/dev\/sdb
\nDevice contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
\nBuilding a new DOS disklabel. Changes will remain in memory only,
\nuntil you decide to write them. After that, of course, the previous
\ncontent won’t be recoverable.<\/p>\n

The number of cylinders for this disk is set to 9039.
\nThere is nothing wrong with that, but this is larger than 1024,
\nand could in certain setups cause problems with:
\n1) software that runs at boot time (e.g., old versions of LILO)
\n2) booting and partitioning software from other OSs
\n(e.g., DOS FDISK, OS\/2 FDISK)<\/p>\n

Command (m for help):<\/p>\n

m will list the options available.
\neg. p will print the partition table, n is for adding new partition table;\u00a0<\/span>
\nand after the changes are done, w will commit the changes, and exit the program.<\/p>\n

e2label<\/span><\/b><\/p>\n

Usage of e2label is simple. manpage for e2label shows following command line options,<\/p>\n

e2label device [ new-label ]<\/p>\n

device can be the entire drive or a partition.
\neg.
\n\/dev\/sda is the entire drive
\n\/dev\/sda1 is the first partition of device \/dev\/sda
\n\/dev\/sda2 is the second partition of device \/dev\/sda<\/p>\n

eg. to show the label of \/dev\/sda1 and \/dev\/sda3<\/p>\n

# e2label \/dev\/sda1
\n\/boot<\/p>\n

# e2label \/dev\/sda3
\n\/<\/p>\n

To change the label for \/dev\/sda3, do as follows,
\n# e2label \/dev\/sda3 changed-label<\/p>\n

and to confirm the change was done sucessfully,
\n# e2label \/dev\/sda3
\nchanged-label<\/p>\n

if you want a \/ in front of the label,<\/p>\n

# e2label \/dev\/sda3 \/changed-label<\/p>\n

to verify that the change was done,<\/p>\n

# e2label \/dev\/sda3
\n\/changed-label<\/p>\n

if you want the server to be able to boot next time round, ensure changes are made to \/etc\/fstab as well. Otherwise, on the next boot, you may be prompted with errors, eg.<\/p>\n

fsck.ext3: Unable to resolve ‘LABEL=\/boot’
\nfsck.ext3: Unable to resolve ‘LABEL=\/’<\/p>\n

in which case, you can boot up with a rescue disk, eg. CentOS installation disk, enter “linux rescue” at prompt; chroot \/mnt\/sysimage and edit \/etc\/fstab accordingly. Alternatively, if you are prompted for root password, and gets a shell, you may be able to edit \/etc\/fstab. If the filesystem is readonly, remount the filesytem readwrite. eg. mount -o remount,rw \/<\/p>\n

mount, umount<\/span><\/b><\/p>\n

# mount \/dev\/sdb5 \/tmp\/mnt<\/p>\n

will mount \/dev\/sdb5 on the \/tmp\/mnt directory
\nif \/tmp\/mnt does not exist, it needs to be created, using mkdir<\/p>\n

to unmount the device, use umount \/dev\/sdb5 or umount \/tmp\/mnt<\/p>\n

Example of partitioning, formatting and labelling of a new drive<\/span><\/b><\/p>\n

2 partitions to be created
\n100MB and rest of the drive<\/p>\n

# fdisk \/dev\/sdb
\nDevice contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
\nBuilding a new DOS disklabel. Changes will remain in memory only,
\nuntil you decide to write them. After that, of course, the previous content won’t be recoverable.<\/p>\n

The number of cylinders for this disk is set to 9039.
\nThere is nothing wrong with that, but this is larger than 1024,
\nand could in certain setups cause problems with:
\n1) software that runs at boot time (e.g., old versions of LILO)
\n2) booting and partitioning software from other OSs
\n(e.g., DOS FDISK, OS\/2 FDISK)<\/p>\n

Command (m for help): n
\nCommand action
\ne extended
\np primary partition (1-4)
\np
\nPartition number (1-4): 1
\nFirst cylinder (1-9039, default 1):
\nUsing default value 1
\nLast cylinder or +size or +sizeM or +sizeK (1-9039, default 9039): +100M<\/p>\n

Command (m for help): n
\nCommand action
\ne extended
\np primary partition (1-4)
\np
\nPartition number (1-4): 2
\nFirst cylinder (14-9039, default 14):
\nUsing default value 14
\nLast cylinder or +size or +sizeM or +sizeK (14-9039, default 9039):
\nUsing default value 9039<\/p>\n

Command (m for help): p<\/p>\n

Disk \/dev\/sdb: 74.3 GB, 74355769344 bytes
\n255 heads, 63 sectors\/track, 9039 cylinders
\nUnits = cylinders of 16065 * 512 = 8225280 bytes<\/p>\n\n\n\n\n\n
Device<\/b><\/td>\nBoot<\/b><\/td>\nStart<\/b><\/td>\nEnd<\/b><\/td>\nBlocks<\/b><\/td>\nId<\/b><\/td>\nSystem<\/b><\/td>\n<\/tr>\n
\/dev\/sda1<\/td>\n<\/td>\n1<\/td>\n13<\/td>\n104391<\/td>\n83<\/td>\nLinux<\/td>\n<\/tr>\n
\/dev\/sda2<\/td>\n<\/td>\n14<\/td>\n9039<\/td>\n72501345<\/td>\n83<\/td>\nLinux<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Command (m for help): w
\nThe partition table has been altered!<\/p>\n

Calling ioctl() to re-read partition table.
\nSyncing disks.<\/p>\n

Next: format both partitions as ext3 filesystems<\/p>\n

# mkfs.ext3 \/dev\/sdb1
\nmke2fs 1.39 (29-May-2006)
\nFilesystem label=
\nOS type: Linux
\nBlock size=1024 (log=0)
\nFragment size=1024 (log=0)
\n26104 inodes, 104388 blocks
\n5219 blocks (5.00%) reserved for the super user
\nFirst data block=1
\nMaximum filesystem blocks=67371008
\n13 block groups
\n8192 blocks per group, 8192 fragments per group
\n2008 inodes per group
\nSuperblock backups stored on blocks:
\n8193, 24577, 40961, 57345, 73729<\/p>\n

Writing inode tables: done
\nCreating journal (4096 blocks): done
\nWriting superblocks and filesystem accounting information: done<\/p>\n

This filesystem will be automatically checked every 22 mounts or
\n180 days, whichever comes first. Use tune2fs -c or -i to override.<\/p>\n

# mkfs.ext3 \/dev\/sdb2
\nmke2fs 1.39 (29-May-2006)
\nFilesystem label=
\nOS type: Linux
\nBlock size=4096 (log=2)
\nFragment size=4096 (log=2)
\n9076736 inodes, 18125336 blocks
\n906266 blocks (5.00%) reserved for the super user
\nFirst data block=0
\nMaximum filesystem blocks=4294967296
\n554 block groups
\n32768 blocks per group, 32768 fragments per group
\n16384 inodes per group
\nSuperblock backups stored on blocks:
\n32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424<\/p>\n

Writing inode tables: done
\nCreating journal (32768 blocks): done
\nWriting superblocks and filesystem accounting information: done<\/p>\n

This filesystem will be automatically checked every 33 mounts or
\n180 days, whichever comes first. Use tune2fs -c or -i to override.<\/p>\n

next: use e2label to label the volumes. Although both mkfs3.ext and\u00a0<\/span>
\ntune2fs is capable of labelling, with the -L option, I am deliberately\u00a0<\/span>
\nusing e2label in this example to demonstrate the use of e2label.<\/p>\n

# e2label \/dev\/sdb1 \/drive2-100MB<\/p>\n

confirm its done.<\/p>\n

# e2label \/dev\/sdb1
\n\/drive2-100MB<\/p>\n

label sdb2 next,<\/p>\n

# e2label \/dev\/sdb2 \/drive2-restofdrive
\nWarning: label too long, truncating.
\n# e2label \/dev\/sdb2
\n\/drive2-restofdr<\/p>\n

the description used was too long, and got truncated. maximum for label is 16 characters.<\/p>\n

next, we try to mount and unmount the 2 filesystems created,<\/p>\n

mount shows what has already been mounted. in addition, the -l option shows the filesystem label<\/p>\n

# mount -l
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\nproc on \/proc type proc (rw)
\nsysfs on \/sys type sysfs (rw)
\ndevpts on \/dev\/pts type devpts (rw,gid=5,mode=620)
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]
\ntmpfs on \/dev\/shm type tmpfs (rw)
\nnone on \/proc\/sys\/fs\/binfmt_misc type binfmt_misc (rw)
\nsunrpc on \/var\/lib\/nfs\/rpc_pipefs type rpc_pipefs (rw)<\/p>\n

We are mainly concerned with the drives, so let’s grep for the relevent entries<\/p>\n

#mount -l | grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]<\/p>\n

We need mount points; the following mount points are created,
\n# mkdir \/mountpt1
\n# mkdir \/mountpt2<\/p>\n

to manually mount the drives,
\n# mount \/dev\/sdb1 \/mountpt1<\/p>\n

check that it is mounted,
\n# mount -l|grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]
\n\/dev\/sdb1 on \/mountpt1 type ext3 (rw) [\/drive2-100MB]<\/p>\n

# mount \/dev\/sdb2 \/mountpt2
\n# mount -l|grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]
\n\/dev\/sdb1 on \/mountpt1 type ext3 (rw) [\/drive2-100MB]
\n\/dev\/sdb2 on \/mountpt2 type ext3 (rw) [\/drive2-restofdr]<\/p>\n

to unmount, use umount
\n# umount \/dev\/sdb1
\n# umount \/dev\/sdb2
\n# mount -l|grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]<\/p>\n

we can also mount the filesystems using the filesystem labels,
\n# mount -L \/drive2-100MB \/mountpt1\/
\n# mount -L \/drive2-restofdr \/mountpt2\/
\n# mount -l |grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]
\n\/dev\/sdb1 on \/mountpt1 type ext3 (rw) [\/drive2-100MB]
\n\/dev\/sdb2 on \/mountpt2 type ext3 (rw) [\/drive2-restofdr]<\/p>\n

unmount can also use the mount point instead of the device, eg.<\/p>\n

# umount \/mountpt1
\n# umount \/mountpt2
\n# mount -l |grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]<\/p>\n

next: edit \/etc\/fstab, add in entries for the new drive if we want it to be mounted at boot up.<\/p>\n

following is existing \/etc\/fstab for the server, which was installed for purpose of this tutorial,<\/p>\n\n\n\n\n\n\n\n\n\n
LABEL=\/<\/td>\n\/<\/td>\next3<\/td>\ndefaults<\/td>\n1<\/td>\n1<\/td>\n<\/tr>\n
LABEL=\/boot<\/td>\n\/boot<\/td>\next3<\/td>\ndefaults<\/td>\n1<\/td>\n2<\/td>\n<\/tr>\n
tmpfs<\/td>\n\/dev\/shm<\/td>\ntmpfs<\/td>\ndefaults<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
devpts<\/td>\n\/dev\/pts<\/td>\ndevpts<\/td>\ngid=5,mode=620<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
sysfs<\/td>\n\/sys<\/td>\nsysfs<\/td>\ndefaults<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
proc<\/td>\n\/proc<\/td>\nproc<\/td>\ndefaults<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
LABEL=SWAP-sda2<\/td>\nswap<\/td>\nswap<\/td>\ndefaults<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

add the following entries,<\/p>\n\n\n\n\n
LABEL=\/drive2-100MB<\/td>\n\/mountpt1<\/td>\next3<\/td>\ndefaults<\/td>\n1<\/td>\n1<\/td>\n<\/tr>\n
LABEL=\/drive2-restofdr<\/td>\n\/mountpt2<\/td>\next3<\/td>\ndefaults<\/td>\n1<\/td>\n2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

mount has a -a option which reads \/etc\/fstab and mounts all filesystems mentioned in the file,<\/p>\n

# mount -a
\n# mount -l |grep \/dev\/sd
\n\/dev\/sda3 on \/ type ext3 (rw) [\/]
\n\/dev\/sda1 on \/boot type ext3 (rw) [\/boot]
\n\/dev\/sdb1 on \/mountpt1 type ext3 (rw) [\/drive2-100MB]
\n\/dev\/sdb2 on \/mountpt2 type ext3 (rw) [\/drive2-restofdr]<\/p>\n

next, reboot, and ensure the new drive is mounted automatically, and accessible via the mount points, \/mountpt1, \/mountpt2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"

Tutorial: e2label, fdisk, \/etc\/fstab, mount, linux rescue, rescue disk, CentOS Let’s run through an example of a fresh disk, that needs to be configured, going through partitioning with fdisk, make filesystem, filesystem labelled using e2label, \/etc\/fstab edited, and mounted using mount. This is relevent for CentOS 3.x, 4.x 5.x; YMMV for other flavours.<\/p>\n

First, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,4],"tags":[],"_links":{"self":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/3129"}],"collection":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3129"}],"version-history":[{"count":2,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/3129\/revisions"}],"predecessor-version":[{"id":3131,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/3129\/revisions\/3131"}],"wp:attachment":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3129"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3129"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3129"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}