sysadmin, you will need to add additional swap space to a box. At that
time, your options will be to use a free disk partition with suitable
space or to create a swapfile on an existing filesystem. The following
details both partition and swapfile with the host info below:
HOST: beastie PROMPT: beastie [0] OS: FreeBSD 8.1PARTITION: If you already have a free partition that isn't being used
for anything else, adding it as swap space is trivial:
beastie [0] /sbin/swapon /dev/da2s1aSince I don't have any free partitions on a configured disk, I need to
create one on an available disk. I check to see what disks the OS can
see via 'gpart' (check 'dmesg' for hosts prior to FreeBSD 7.0):
beastie [0] /sbin/gpart show | /usr/bin/grep '=>' => 63 21493647 da0 MBR (10G) => 63 21495726 da1 MBR (10G) => 0 21478842 da0s1 BSD (10G) => 0 21478842 da1s1 BSD (10G) => 32 1048544 da2 MBR (512M) => 32 1048544 da3 MBR (512M)I already know I'm not using 'da2' and from the above 'gpart' doesn't
show any slices for it, so we can use it to set up 'da2' for our new
swap partition:
beastie [0] /bin/dd if=/dev/zero of=/dev/da2 bs=512 count=32 32+0 records in 32+0 records out 16384 bytes transferred in 0.017235 secs (950621 bytes/sec) beastie [0] /sbin/fdisk -BI /dev/da2 ******* Working on device /dev/da2 ******* fdisk: invalid fdisk partition table found fdisk: Class not found beastie [0] /sbin/bsdlabel -w da2s1 beastie [0] /sbin/bsdlabel -A da2s1 # /dev/da2s1: type: unknown disk: amnesiac label: flags: bytes/sector: 512 sectors/track: 32 tracks/cylinder: 64 sectors/cylinder: 2048 cylinders: 511 sectors/unit: 1048544 rpm: 3600 interleave: 1 trackskew: 0 cylinderskew: 0 headswitch: 0 # milliseconds track-to-track seek: 0 # milliseconds drivedata: 0 8 partitions: # size offset fstype [fsize bsize bps/cpg] a: 1048528 16 unused 0 0 c: 1048544 0 unused 0 0 # "raw" part, don't editIn the first command above, we've used 'dd' to destroy the boot block
and partition data on 'da2', then re-initialized the disk with 'fdisk'
in the second command. This set up slice 1 (s1). The errors from
'fdisk' are normal, simply telling you that before initializing 'da2',
fdisk couldn't read a valid partition table. The "Class" error is because
'geom_mbr' isn't loaded, which can be safely ignored. Following that,
the third command writes a generic partition table to 'da2s1' and the
fourth is simply verifying such. The following adds the new partition
as swap space and shows the configured swap space before and after adding
'da2s1a':
beastie [0] /sbin/swapon /dev/da2s1a before adding: beastie [0] /usr/sbin/swapinfo Device 1K-blocks Used Avail Capacity /dev/da0s1b 1048576 0 1048576 0% after adding: beastie [0] /usr/sbin/swapinfo Device 1K-blocks Used Avail Capacity /dev/da0s1b 1048576 0 1048576 0% /dev/da2s1a 524264 0 524264 0% Total 1572840 0 1572840 0%To retain the freshly added space through a system reboot, add 'da2s1a'
to /etc/fstab as seen below:
beastie [0] /usr/bin/grep swap /etc/fstab /dev/da0s1b none swap sw 0 0 /dev/da2s1a none swap sw 0 0SWAPFILE: For the second option, locate an out of the way place on a
filesystem with adequate space for the swap file. For our purposes,
we'll use '/opt/swapfile' for a new 512 MB swap file. Below simply
checks to make sure that it doesn't already exist after ensuring the
directory exists:
beastie [0] [ ! -d /opt ] && /bin/mkdir /opt beastie [0] /bin/ls /opt/swapfile ls: /opt/swapfile: No such file or directoryNow, use 'dd' to create '/opt/swapfile' with a size of 512 MB:
beastie [1] /bin/dd if=/dev/zero of=/opt/swapfile bs=1k count=512k 524288+0 records in 524288+0 records out 536870912 bytes transferred in 13.871350 secs (38703580 bytes/sec) beastie [0] /usr/bin/du -sh /opt/swapfile 512M /opt/swapfile beastie [0] /bin/chown root:wheel /opt/swapfile beastie [0] /bin/chmod 600 /opt/swapfileAfter file creation, we've verified the file and size and updated it
with appropriate permissions. The next step is use 'mdconfig' to create
a block device for '/opt/swapfile' and verify the device's creation:
beastie [0] /sbin/mdconfig -l beastie [0] /sbin/mdconfig -a -t vnode -f /opt/swapfile -u 0 beastie [0] /sbin/mdconfig -l md0Like with a swap partition, we can use 'swapon' to add block device
'/dev/md0' as usable swap space:
beastie [0] /sbin/swapon /dev/md0 beastie [0] /usr/sbin/swapinfo Device 1K-blocks Used Avail Capacity /dev/da0s1b 1048576 0 1048576 0% /dev/da2s1a 524264 0 524264 0% /dev/md0 524288 0 524288 0% Total 2097128 0 2097128 0%To retain the swap file through a system reboot, update '/etc/rc.conf':
beastie [0] /usr/bin/grep swapfile /etc/rc.conf swapfile="/opt/swapfile"
see also:
Adding Swap Space in Solaris
Adding Swap Space in Linux
