Upload
rajeev-ghosh
View
214
Download
0
Embed Size (px)
DESCRIPTION
Practical Guide to AIX Filesystems
Citation preview
AIX FileSystems:
Contents
1. Creation of Filesystem
2. Mount/Unmount Filesystem
3. List Filesystems
4. Display Filesystem usage
5. Resize Filesystems
6. Modify/Change Filesystem
7. Remove Filesystems
8. Freeze File System
9. Split mirrored copy from FS
10. defrag filesystem
11. fuser & file systems
12. Filesystem Checking & Repairing
13. Miscellaneous Filesystem Commands
1) Creation of Filesystem:
The crfs command creates a file system on a logical volume within a previously created volume group.
A new logical volume is created for the file system unless the name of an existing logical volume is specified using the -d. An entry for the file system is put into the /etc/filesystems file.
Commands##With an existing logical volume: # crfs -v jfs2 -d <lv> -m <mountpoint> -A yes -v vfs type (Specifies the virtual file system type) -d Specifies the device name of a device or logical volume on which to make the file system. -m Specifies the mount point, which is the directory where the file system will be made available -A Specifies whether the file system is mounted at each system restart: yes:File system is automatically mounted at system restart. no:File system is not mounted at system restart (default value).
Note: start of changeThe crfs command accesses the first letter for the auto mount -A option.end of change
## Create logical volume, filesystem, mountpoint, add entry to /etc/filesystems at the specified size
# crfs -v jfs2 -g <vg> -m <mountpoint> -a size=<size in 512k blocks|M|G) -A yes
Note: there are two types of filesystems jfs and jfs2, jfs2 allows you to decrease the filesystem size , you cannot reduce a jfs filesystem.
2) mount/unmount Filesystems:
mount is the command used to mount filesystems
mount [<fs>|<lv>]
mount –a >> Mount all filesystems mentioned in /etc/filesystems.
mount all
To unmount filesystem use "umount"
umount <fs>
Note: You can't write into or read any content from filesystem when its in unmounted
state
-f unmount filesystem forcibly
umount -f <fs>
for v7.1 onwards you can use name for "unmount" command as well.
umountall: Unmounts groups of dismountable devices or filesystems ( applicable to
v7.1)
3) List Filesystems:
To list filesysem use "lsfs" or "mount"
lsfs Lists all filesystems in the /etc/filesystems entry
lsfs -a To list all filesystems (default)
lsfs -q <fs> (detailed)
lsfs -q List all filesystems with detailed info (shows size of FS and LV in it. so we
can check whether size of LV=size os FS)
lsfs -l Specify the output in list format
lsfs -c Specify the output in column format
lsfs -v jfs Lists all jfs filesystems
mount (to list all mounted filesystems)
mount <fs> ( to list the mounted filesysem)
Note: use the '-q' to see if the logical volume size is bigger than the filesystem
size
4) Display Filesystem usage:
To display information about all mounted file systems, enter: df
Command Examples1) If your system has the /, /usr, /site, and /usr/venus file systems mounted, the output from the df command resembles the following:
df
Filesystem 512-blocks Free %Used Iused %Iused Mounted on/dev/hd0 19368 9976 48% 4714 5% //dev/hd1 24212 4808 80% 5031 19% /usr/dev/hd2 9744 9352 4% 1900 4% /site/dev/hd3 3868 3856 0% 986 0% /usr/venus
2) To display information about /test file system in 1024-byte blocks, enter:
df -k /test
Filesystem 1024 blocks Free %Used Iused %Iused Mounted on/dev/lv11 16384 15824 4% 18 1% /tmp/ravi1
This displays the file system statistics in 1024-byte disk blocks.
3) To display information about /test file system in MB blocks, enter:df -m /test
Filesystem MB blocks Free %Used Iused %Iused Mounted on/dev/lv11 16.00 15.46 4% 18 1% /tmp/ravi1
This displays file system statistics in MB disk blocks rounded off to nearest 2nd decimal digit.
4) To display information about the /test file system in GB blocks, enter:
df -g /test
Filesystem GB blocks Free %Used Iused %Iused Mounted on/dev/lv11 0.02 0.02 0% 18 1% /tmp/ravi1
This displays file system statistics in GB disk blocks rounded off to nearest 2nd decimal digit.
5) Resize Filesystems:
chfs -a size=<new size> <fs>
Command Exampleschfs -a size=1G /var (specific size, can be used to increase and decrease) chfs -a size=+1G /var (increase by 1GB) chfs -a size=-1GB /var (reduce by 1GB)
Note1:This will automatically increase or decrease the underlying logical volume as well. Note2:You can't reduce jfs filesystem
6) Modify/Change Filesystems:
Command Examples## Change the mountpoint
chfs -m <new mountpoint> chfs -m /test /new ==>Change the mount point from /test to /new
## Do not mount after a restart
chfs -A no <fs> ## Mount read-only
chfs -p ro <fs>## Remvoe attribute of a filesystem
Remove account attribute of /test.(from /etc/filesystems file)
chfs -d account /test chfs -a options='rw' /shadow ==> shows with lsfs rw (I think rw is the deafault anyway)
7) Remove Filesystems:
Command Examplesrmfs <fs> rmfs -r /test ==>Deletes FS /test its mount point and associated LV
Note1: You need to unmount the filesyem before removing.Note2: if all filesystems have been removed from a logical volume then the logical volume is removed as well.
8) Freeze File System:
If you don't want your file system to perform any writes for a period of time, maybe due to an admin task like a split copy or a backup, you can freeze the file system. After the admin tasks are completed, you can thaw the file system. chfs -a freeze=<time in seconds> <fs>
chfs -a freeze=off <fs>
9) Split mirrored copy of filesystem:
chfs -a splitcopy=<split copy mountpoint> -a copy=2 <fs>
chfs -a splitcopy=/backup -a copy=2 /testfs
This will mount the 2nd copy of mirrored filesystem testfs to /backup in read-only
mode for backup purpose
10) defrag fielsystem:
The defragfs command can be used to improve or report the status of contiguous space within a file system.
Command Examplesdefragfs /test ==>To defragment the file system /testdefragfs -q /test ==>Display the current defrag status of the file system
For example, to defragment the file system /home, use the following command:
defragfs /home
Here is an example output:
# defragfs /homeDefragmenting device /dev/hd1. Please wait.
Total allocation groups : 32Allocation groups skipped - entirely free : 26Allocation groups defragmented : 6defragfs completed successfully.
Total allocation groups : 32Allocation groups skipped - entirely free : 26Allocation groups that are candidates for defragmenting : 6Average number of free runs in candidate allocation groups : 1#
11) fuser & filesystem:
Command Examplesfuser /etc/passwd lists the process numbers of local processes using the /etc/passwd file
fuser -cux /var shows which processes are using the given filesystem
fuser -cuxk /var it will kill the above processes
fuser -dV /tmp shows deleted files (inode) with process ids which were open by a process (so its space could not be freed up)
(-V: verbose will show the size of the files as well)if we rm a file, while it is opened by a process its space will not free up. solution: kill the process, wait for the process to finish or reboot the system
12) Checking and Repairing:
Command Examplesfsck [-y|-n] <fs> (check a filesystem)
fsck -p lt;fs> (restores primary superblock from backup copy if corrupt)
fsck -y n /dev/lv00 ==>To check the filesystem associated to /dev/lv00 assuming response "yes"
13) Miscellaneous Filesystem Commands:
Command Examplesskulker ==> cleans up file systems by removing unwanted or obsolete files
fileplace <filename> ==> displays the placement of file blocks within logical or physical volumes, it will show if a file fragmented