|
|
Running out of /usr space ...
|
|
|
|
swapon(8) System Manager's Manual swapon(8) NAME
swapon - Specifies additional disk partitions for paging and swapping SYNOPSIS
/sbin/swapon [-asv] [-s special-device] [-v special-device] DESCRIPTION
The swapon command is used to specify additional disk partitions for paging and swapping. A paging partition is a block special device. ( Tru64 UNIX does not currently support paging and swapping to a regular file. All paging and swapping areas must be block special devices.) The swapon command uses a priority default of 4 for block special devices. Calls to swapon normally occur in the system multiuser state initialization. When you make more swap space available with the command, the additional swap space is available until the system is rebooted. To make additional swap space permanent, you must specify the swap device entry in the /etc/sysconfigtab file. The swapon command flags can override the partition specifications in the /etc/sysconfigtab file. You can use Logical Storage Manager (LSM) volumes for additional swap space. For high system availability, you can mirror the LSM volumes. The Logical Storage Manager manual describes how to use the command to configure an LSM mirrored volume as additional swap space. There are two strategies for swap space allocation: immediate mode and deferred or over-commitment mode. The two strategies differ in the point in time at which swap space is allocated. If immediate mode is used, swap space is allocated when modifiable virtual address space is created. If deferred mode is used, swap space is not allocated until the system needs to write a modified virtual page to swap space. Immediate mode is the default swap space allocation strategy. Immediate mode is more conservative than deferred mode because each modifiable virtual page is assigned a page of swap space when it is created. If you use the immediate mode of swap space allocation, you must allocate a swap space that is at least as large as the total amount of modifiable virtual address space that will be created on your system. Immediate mode requires significantly more swap space than deferred mode because it guarantees that there will be enough swap space if every modifiable virtual page is modified. If you use the deferred mode of swap space allocation, you must estimate the total amount of virtual address space that will be both cre- ated and modified, and compare that total amount with the size of your system's physical memory. If this total amount is greater than the size of physical memory, the swap space must be large enough to hold the modified virtual pages that do not fit into your physical memory. If your system's workload is complex and you are unable to estimate the appropriate amount of swap space by using this mode, you should first use the default amount of swap space and adjust the swap space as needed. To determine which swap space allocation mode is being used, check the setting of the vm-swap-eager parameter in /etc/sysconfigtab. If it is either not specified or set to 1, the system uses immediate swap mode. If it is set to 0 (zero), the system uses deferred mode. FLAGS
Installs all paging partitions specified in the /etc/sysconfigtab file. Displays swap space utilization. For each swap partition, this flag displays the total amount of allocated swap space, the amount of swap space that is being used, and the amount of free swap space. Generates verbose output. NOTES
There is no way to stop paging and swapping on a partition. It is therefore not possible to use swap devices that can be dismounted during system operation. Swap space is also used during a system crash dump. In planning your swap space allocation you should also consider your crash dump requirements. See the System Administration for information on crash dumps. EXAMPLES
The following example shows a swap device entry in an /etc/sysconfigtab file: vm: swapdevice=/dev/disk/dsk0b,/dev/disk/dsk1b The following command adds the /dev/disk/dsk0b block device file as swap space: swapon /dev/disk/dsk0b ERRORS
You may receive the following messages when using the swapon command: special-device or an overlapping partition is open. Quitting... This message indicates that you tried to add a partition as a swap device that is actively in use by UFS, AdvFS, swap, or LSM. spe- cial-device is marked in use for fstype in the disklabel. If you continue with the operation you can possibly destroy existing data. CONTINUE? [y/n] This message indicates that you tried to use a partition as a swap device that is not currently in active use but is marked for use in the disk label's partition map. For example, the partition may be part of an LSM volume or an AdvFS domain. If you know that the partition you specified to swapon does not contain any data, you can choose to override the warning. In this case, the fstype in the disk label will be modified to swap. Note that you can use the disklabel -s command to set the fstype in the disk label to unused for partitions that do not contain any valid data. See disklabel(8) for more information. Partition(s) which overlap special-device are marked in use. If you continue with the operation you can possibly destroy existing data. CONTINUE? [y/n] This message indicates that the partition you specified is not marked for use, but other, overlapping partitions on the disk are marked for use. If you override this warning, the fstype in the disk's label will be modified. The partition you specified to swapon will be marked as in use as a swap device and all overlapping partitions will be marked UNUSED. The following examples illustrate these messages: Adding a partition that is marked for use as a swap device: # /usr/sbin/swapon /dev/disk/dsk11g /dev/disk/dsk11g disk is marked in use for LSMpubl in the disklabel. If you continue with the operation you can possibly destroy existing data. CONTINUE? [y/n] Partition g of disk dsk11 is part of a disk marked for use by LSM. If LSM is not actively using this partition and the partition does not contain any data, you may want to override this warning, by answering y. In this case, partition g will be marked as swap in the disk label. Adding a partition as a swap device whose overlapping partitions are marked for use: # /usr/sbin/swapon /dev/disk/dsk11c Partition(s) which overlap /dev/disk/dsk11c are marked in use. If you continue with the operation you can possibly destroy existing data. CONTINUE? [y/n] If you answer yes, partition c on disk dsk11 will be marked swap in the disk label and all partitions that overlap c will be marked UNUSED. Adding a partition that is currently in use as a swap device: # /usr/sbin/swapon /dev/disk/dsk11g /dev/disk/dsk11g or an overlapping partition is open. Quitting... Adding a partition that does not have a disk label as a swap device: # /usr/sbin/swapon /dev/disk/dsk11c The disklabel for /dev/disk/dsk11c does not exist or is corrupted. Quitting... See disklabel(8) for information on installing a disk label on a disk. FILES
Specifies the command path. Specifies information about file systems and swap devices. RELATED INFORMATION
Functions: swapon(2), savecore(8) System Administration delim off swapon(8)
