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cwng
n00b
Joined: 21 Nov 2002
Posts: 68
Location: Singapore
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 Posted: Tue Jan 25, 2005 4:18 am Post subject: Using tmpfs for /var/{log,lock,...} |
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EDIT: A new, simplified version
The following is a new simplified version. The original post is moved to subsequent post (3 or 4 post down).
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The thread in Using tmpfs for /tmp prompted me to experiment with using tmpfs for some /var directories that has frequent disk read/write, such as /var/log. I imagine doing so will have certain advantages:
- Speed: it speeds up the logging process
- I/O: it reduces disk I/O
The following are the scripts I have conjured, to see if anyone brave enough to try them. I have been using them for a while, no problems so far.
/etc/init.d/vartmp - This is the startup script:
| Code: |
#!/sbin/runscript
#
# This init script mounts various /var sub-directories into RAM-based filesystem
# (i.e. tmpfs). There are two main advantages in doing so:
# - speed: its speeds up logging processes
# - disk-sync: it reduces the need for constant disk syncs
#
# and make sure the ${VARTMP} directory is created and/or mounted before
# executing this script.
depend() {
need localmount
before bootmisc
}
start() {
ebegin "Migrating /var to tmpfs "
#
# Check existence of ${VARTMP}
#
if [ -z ${VARTMP} ]; then
VARTMP=/dev/shm/vartmp
fi
if [ ! -d ${VARTMP} ]; then
mkdir ${VARTMP}
fi
for d in ${VARTMP_DIRS}; do
move_to_vartmp ${d}
done
eend $?
}
stop() {
ebegin "Syncing /var from tmpfs "
if [ -z ${VARTMP} ]; then
VARTMP=/dev/shm/vartmp
fi
for d in ${VARTMP_DIRS}; do
move_from_vartmp ${d}
done
eend $?
}
# This function transfer /var/* to ${VARTMP}
move_to_vartmp() {
ebegin "Moving /var/${1} to ${VARTMP}/${1} "
#
# Move /var/xxx contents to ${VARTMP}
#
if [ -e /var/${1} ]; then
mv /var/${1} ${VARTMP}
ln -sf ${VARTMP}/${1} /var/${1}
else
if [ ! -d ${VARTMP}/${1} ]; then
rm -f ${VARTMP}/${1}
mkdir ${VARTMP}/${1}
chmod 775 ${VARTMP}/${1}
fi
fi
eend $?
}
# This function transfer ${VARTMP} back to /var
move_from_vartmp() {
ebegin "Moving ${VARTMP}/${1} back to /var/${1} "
if [ -d ${VARTMP}/${1} ]; then
if [ -e /var/${1} ]; then
rm -f /var/${1}
fi
mv ${VARTMP}/${1} /var/
fi
eend $?
}
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/etc/conf.d/vartmp - This is the configuration file:
| Code: |
# /etc/conf.d/vartmp
#
# VARTMP defines where the tmpfs base directory for /var is
VARTMP="/dev/shm/vartmp"
# VARTMP_DIRS defines which of the /var sub-directories resides on the tmpfs
VARTMP_DIRS="log lock run"
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Steps - Here is what I did:
First, edit /etc/conf.d/vartmp to your liking (particularly the VARTMP_DIRS="" variable that specify which of the subdirectories to move to tmpfs. You definitely don't want to move all of them, unless you have obscene amount of RAM, like 32G  ) and run the init script:
| Code: | rc-update add vartmp boot
/etc/init.d/vartmp start
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For me, I will see this:
| Code: | bach cwng # rc-update add vartmp boot
* vartmp added to runlevel boot
* Caching service dependencies...
* rc-update complete.
bach cwng # /etc/init.d/vartmp start
* Migrating /var to tmpfs ...
* Moving /var/log to /dev/shm/vartmp/log [ ok ]
* Moving /var/lock to /dev/shm/vartmp/lock [ ok ]
* Moving /var/run to /dev/shm/vartmp/run [ ok ]
bach cwng # ls -l /var
total 0
drwxr-xr-x 6 root root 74 Dec 21 00:21 cache
drwxr-xr-x 3 root root 16 Oct 28 14:36 db
drwxr-xr-x 2 root root 18 Jan 4 11:10 empty
drwxrwx--T 2 root gdm 18 Jan 10 22:45 gdm
drwxr-xr-x 13 root root 150 Dec 29 19:40 lib
lrwxrwxrwx 1 root root 15 Jan 25 16:48 lock -> /dev/shm/vartmp/lock
lrwxrwxrwx 1 root root 15 Jan 25 16:48 log -> /dev/shm/vartmp/log
lrwxrwxrwx 1 root root 15 Dec 20 19:06 mail -> /var/spool/mail
lrwxrwxrwx 1 root root 15 Jan 25 16:48 run -> /dev/shm/vartmp/run
drwxr-xr-x 8 root root 92 Jan 14 16:25 spool
drwxr-xr-x 2 root root 18 Oct 28 14:23 state
drwxrwxrwt 5 root root 93 Jan 24 15:05 tmp
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Well, all seems fine. If for any reason you wish to revert back to the original setting, you just have to do:
| Code: | /etc/init.d/vartmp stop
rc-update del vartmp
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Some suggestions from freeix (see his post below for detail)
- Specify PORT_LOGDIR in /etc/make.conf to avoid having a huge emerge.log in RAM.
- You can move /var/tmp to tmpfs as well, but you may want to specify PORTAGE_TMPDIR in /etc/make.conf to avoid having the entire portage working directories on RAM.
WARNING: Doing so may cause loss of log files when system is hang, or looses power. As freeix suggested, you may wish to symlink /var/log/critical to somewhere else.
/rgds
/cwng
Last edited by cwng on Wed Jan 26, 2005 2:27 am; edited 5 times in total |
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Gherald
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Joined: 23 Aug 2004
Posts: 1399
Location: CLUAConsole
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| Posted: Tue Jan 25, 2005 5:05 am Post subject: |
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You are my hero! err, that is to say, this is exactly the sort of thing I was planning to write myself
A few quick notes:
- I recommend using /dev/shm. May as well get some use out of it.
- Back up your /var/log before proceeding, and make sure it is of reasonable size!
- If you have set PORT_LOGDIR=/var/log/emerge in make.conf, you probably want to change this to /var/portage/log or somesuch (create the appropriate directories, of course). In my case /var/log/emerge was over 200MB, and you don't want that sitting in your ram!
PORT_LOGDIR is a very useful feature, btw. Well worth checking out when you need to see why an ebuild failed.
- It is probably worth including /var/tmp as well. Just not /var/tmp/portage. So change PORTAGE_TMPDIR in make.conf from "/var/tmp" to "/var/portage" (and create the portage directory, if you haven't already). |
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cwng
n00b
Joined: 21 Nov 2002
Posts: 68
Location: Singapore
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| Posted: Tue Jan 25, 2005 7:19 am Post subject: |
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| freeix wrote: | | - I recommend using /dev/shm. May as well get some use out of it. |
True, unless you have programs running that do a lot of shared memory. That's why if you don't specify VARTMP_MOUNT, it is defaulted to /dev/shm/vartmp.
Your insights into PORT_LOGDIR and PORTAGE_TMPDIR are all very true. For directories that may grew very large and you don't want them to be in tmpfs, one method is to soft-link the directory to somewhere else, eg:
| Code: | mv /var/log/samba /somewhere-else-on-disk/
ln -sf /somewhere-else-on-disk/samba /var/log/samba
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There is one more caution I wish to make: if for any reason, your power is tripped or the whole system hangs, you will lose all the changes to your /var/xxx files since the system last booted. This shouldn't be an issue for /var/run and /var/locks. But you may loose some of the log files that may prove critical to providing information on why your system hanged. |
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Gherald
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Joined: 23 Aug 2004
Posts: 1399
Location: CLUAConsole
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| Posted: Tue Jan 25, 2005 7:51 am Post subject: |
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The best solution is probably to use metalog and link /var/log/critical to disk.
For samba, you can set the maximum log size to something reasonable like 100k |
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