Posts Tagged ‘partition’

How to check Linux OS install date / How long ago was Linux installed

Sunday, October 22nd, 2017

If you're sysadmin who inherited a few hundreds of Linux machines from a previous admin and you're in process of investigating how things were configured by the previous administrator one of the crucial things to find out might be

How Long ago was Linux installed?

Here is how to check the Linux OS install date.

The universal way nomatter the Linux distribution is to use fullowing command:

 

root@pcfreak:~# tune2fs -l /dev/sda1 | grep 'Filesystem created:'
Filesystem created:       Thu Sep  6 21:44:22 2012

 

 

Above command assumes the Linux's root partition / is installed on /dev/sda1 however if your case is different, e.g. the primary root partition is installed on /dev/sda2 or /dev/sdb1 / dev/sdb2 etc. just place the right first partition into the command.

If primary install root partition is /dev/sdb1 for example:
 

root@pcfreak:~# tune2fs -l /dev/sdb1 | grep 'Filesystem created:'

 


To find out what is the root partition of the Linux server installed use fdisk command:

 

 

 

root@pcfreak:~# fdisk -l

 

Disk /dev/sda: 465,8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00051eda

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sda1  *         2048 965193727 965191680 460,2G 83 Linux
/dev/sda2       965195774 976771071  11575298   5,5G  5 Extended
/dev/sda5       965195776 976771071  11575296   5,5G 82 Linux swap / Solaris

Disk /dev/sdb: 111,8 GiB, 120034123776 bytes, 234441648 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

 


Other ways to check the Linux OS install date on Debian / Ubuntu / Mint etc. deb. based GNU / Linux

 


Deban based Linux distributions do create an initial /var/log/installer directory containing various install information such as hardware-summary, partition, initial installed deb packages, exact version of Linux distribution, and the way it was installed either it was installed from an ISO image, or it was network install etc.

 

root@pcfreak:~# ls -al /var/log/installer/
total 1228
drwxr-xr-x  3 root root   4096 sep  6  2012 ./
drwxr-xr-x 72 root root  12288 окт 22 06:26 ../
drwxr-xr-x  2 root root   4096 sep  6  2012 cdebconf/
-rw-r–r–  1 root root  17691 sep  6  2012 hardware-summary
-rw-r–r–  1 root root    163 sep  6  2012 lsb-release
-rw——-  1 root root 779983 sep  6  2012 partman
-rw-r–r–  1 root root  51640 sep  6  2012 status
-rw——-  1 root root 363674 sep  6  2012 syslog

 

If those directory is missing was wiped out by the previous administrator, to clear up traces of his previous work before he left job another possible way to find out exact install date is to check timestamp of /lost+found directory;
 

root@pcfreak:~# ls -ld /lost+found/
drwx—— 2 root root 16384 sep  6  2012 /lost+found//

 

Check OS Linux install date on (Fedora, CentOS, Scientific Linux, Oracle and other Redhat RPM based Distros)

 

[root@centos: ~]# rpm -qi basesystem
Name        : basesystem
Version     : 10.0
Release     : 7.el7
Architecture: noarch
Install Date: Mon 02 May 2016 19:20:58 BST
Group       : System Environment/Base
Size        : 0
License     : Public Domain
Signature   : RSA/SHA256, Tue 01 Apr 2014 14:23:16 BST, Key ID     199e2f91fd431d51
Source RPM  : basesystem-10.0-7.el7.src.rpm
Build Date  : Fri 27 Dec 2013 17:22:15 GMT
Build Host  : ppc-015.build.eng.bos.redhat.com
Relocations : (not relocatable)
Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
Vendor      : Red Hat, Inc.
Summary     : The skeleton package which defines a simple Red Hat Enterprise Linux system
Description :
Basesystem defines the components of a basic Red Hat Enterprise Linux
system (for example, the package installation order to use during
bootstrapping). Basesystem should be in every installation of a system,
and it should never be removed.

 

How to disable GNOME popup notification in Debian Wheezy Linux

Friday, August 2nd, 2013

how to disable remove GNOME 2 / 3 popup e mail notification  Debian Ubuntu Linux screenshot

I found it very annoying to have a pop-up notification every time I receive a new email it is just pointless there especially, when I already use Thunderbird (IceDove) to fetch my email via pop3. This pop-up notification though planned to be useful messes with my Desktop and breaks the habit on how I'm used to old GNOME interface…. I remember same popup notification was present on older Fedora releases (back in time when I used Fedora Linux for my Desktop).

disable Gnome popup notification new email Debian GNU Linux Wheezy 7 screenshot

My logical guess was in order to disable popup notification in GNOME 3 I had to tamper with gconf-editor. In gconf-editor config database there is:

Apps -> Notification daemon

Problem it is not possible to turn it off. Only available change options are:

default-sound, popup_location, sound_enabled, and theme

After some time of try / fail attempts I found the solution on linuxquestions forum, its quite raw solution but it works, all I had to do is change permissions of /usr/lib/notification-daemon/notification-daemon;

debian:~# chmod 0000 /usr/lib/notification-daemon/notification-daemon

Another thing that is handy to disable is POP UP Window with warning that you have low disk space on Hard Drive.

The warinng for Disk space is very annoying and popups up on every GNOME boot. Actually the hard drive with Low disk space is and old mounted partition in NTFS and I only use it to read data.

Here is how to disable HDD Notification Warnings in GNOME:

debian:~# chmod 0000 /usr/lib/gnome-disk-utility/gdu-notification-daemon

How to mount NTFS Windows XP filesystem on FreeBSD, NetBSD, OpenBSD

Friday, May 11th, 2012

Mounting NTFS hdd partitions on FreeBSD logo picture

A friend of mine bring home a Seagate External Hard Disk Drive using USB 3 as a communication media. I needed to attach the hard disk to my FreeBSD router to transfer him some data, the External HDD is formatted to use NTFS as a main file partition and hence to make the file transfers I had to somehow mount the NTFS partition on the HDD.

FreeBSD and other BSDs, just like Linux does not have embedded NTFS file system mount support.
In order to add an external write support for the plugged hdd NTFS I looked in the ports tree:

freebsd# cd /usr/ports
freebsd# make search name='ntfs'
Port: fusefs-ntfs-2010.10.2
Path: /usr/ports/sysutils/fusefs-ntfs
Info: Mount NTFS partitions (read/write) and disk images
Maint: ports@FreeBSD.org
B-deps: fusefs-libs-2.7.4 libiconv-1.13.1_1 libtool-2.4 libublio-20070103 pkg-config-0.25_1
R-deps: fusefs-kmod-0.3.9.p1.20080208_7 fusefs-libs-2.7.4 libiconv-1.13.1_1 libublio-20070103 pkg-config-0.25_1
WWW: http://www.tuxera.com/community/

Port: ntfsprogs-2.0.0_1
Path: /usr/ports/sysutils/ntfsprogs
Info: Utilities and library to manipulate NTFS partitions
Maint: ports@FreeBSD.org
B-deps: fusefs-libs-2.7.4 libiconv-1.13.1_1 libublio-20070103 pkg-config-0.25_1
R-deps: libublio-20070103 pkg-config-0.25_1
WWW: http://www.linux-ntfs.org/
freebs# cd sysutils/fusefs-ntfs/
freebsd# ls
Makefile distinfo files/ pkg-descr pkg-plist
freebsd# cat pkg-descr
The ntfs-3g driver is an open source, freely available read/write NTFS
driver, which provides safe and fast handling of the Windows XP, Windows
Server 2003 and Windows 2000 filesystems. Almost the full POSIX filesystem
functionality is supported, the major exceptions are changing the file
ownerships and the access rights.
WWW: http://www.tuxera.com/community/

Using ntfs-3g I managed to succeed mounting the NTFS on my old PC running FreeBSD ver. 7_2

1. Installing fuserfs-ntfs support on BSD

Before I can use ntfs-3g, to mount the paritition, I had to install fuserfs-ntfs bsd port, with:

freebsd# cd /usr/ports/sysutils/fusefs-ntfs
freebsd# make install clean
.....

I was curious if ntfsprogs provides other utilities to do the ntfs mount but whilst trying to install it I realized it is already installed as a dependency package to fusefs-ntfs.

fusefs-ntfs package provides a number of utilities for creating, mounting, fixing and doing various manipulations with Microsoft NTFS filesystems.

Here is a list of all the executable utilities helpful in NTFS fs management:

freebsd# pkg_info -L fusefs-ntfs\* | grep -E "/bin/|/sbin|README"
/usr/local/bin/lowntfs-3g
/usr/local/bin/ntfs-3g
/usr/local/bin/ntfs-3g.probe
/usr/local/bin/ntfs-3g.secaudit
/usr/local/bin/ntfs-3g.usermap
/usr/local/bin/ntfscat
/usr/local/bin/ntfscluster
/usr/local/bin/ntfscmp
/usr/local/bin/ntfsfix
/usr/local/bin/ntfsinfo
/usr/local/bin/ntfsls
/usr/local/sbin/mkntfs
/usr/local/sbin/ntfsclone
/usr/local/sbin/ntfscp
/usr/local/sbin/ntfslabel
/usr/local/sbin/ntfsresize
/usr/local/sbin/ntfsundelete
/usr/local/share/doc/ntfs-3g/README
/usr/local/share/doc/ntfs-3g/README.FreeBSD

The README and README.FreeBSD are wonderful, reading for those who want to get more in depth knowledge on using the up-listed utilities.

One utility, worthy to mention, I have used in the past is ntfsfix. ntfsfix resolve issues with NTFS partitions which were not unmounted on system shutdown (electricity outage), system hang up etc.

2. Start fusefs (ntfs) and configure it to auto load on system boot

Once fuserfs-ntfs is installed, if its necessery ntfs fs mounts to be permanently supported on the BSD system add fusefs_enable="YES" to /etc/rc.conf(the FreeBSD services auto load conf).

freebsd# echo 'fusefs_enable="YES"' >> /etc/rc.conf

One note to make here is that you need to have also dbus_enable="YES" and hald_enable="YES" in /etc/rc.conf, not having this two in rc.conf will prevent fusefs to start properly. Do a quick grep to make sure this two variables are enabled:

Afterwards fsusefs load up script should be run:

freebsd# /usr/local/etc/rc.d/fusefs start
Starting fusefs.

Another alternative way to load ntfs support on the BSD host is to directly load fuse.ko kernel module:

freebsd# /sbin/kldload fuse.ko

3. Mounting the NTFS partition

In my case, the Seagate hard drive was detected as da0, where the NTFS partition was detected as s1 (da0s1):

freebsd# dmesg|grep -i da0
da0 at umass-sim0 bus 0 target 0 lun 0
da0: Fixed Direct Access SCSI-4 device
da0: 40.000MB/s transfers
da0: 953869MB (1953525164 512 byte sectors: 255H 63S/T 121601C)br />GEOM_LABEL: Label for provider da0s1 is ntfs/Expansion Drive.
GEOM_LABEL: Label for provider da0s1 is ntfs/Expansion Drive.

Therefore further to mount it one can use mount_ntfs (to quickly mount in read only mode) or ntfs-3g for (read / write mode):

If you need to just quickly mount a disk drive to copy some data and umount it with no need for writting to the NTFS partition do;

freebsd# /sbin/mount_ntfs /dev/ad0s1 /mnt/disk

Note that mount_ntfs command is a native BSD command and have nothing to do with ntfs-3g. Therefore using it to mount NTFS is not the same as mounting it via ntfs-3g cmd

freebsd# /usr/local/bin/ntfs-3g -o rw /dev/da0s1 /mnt/disk/

Something, I've noticed while using ntfs-3g is, it fails to properly exit even when the ntfs-3g shell execution is over:

freebsd# ps ax |grep -i ntfs|grep -v grep
18892 ?? Is 0:00.00 /usr/local/bin/ntfs-3g -o rw /dev/da0s1 /mnt/disk/

I dunno if this is some kind of ntfs-3g bug or feature specific to all versions of FreeBSD or it is something local to FBSD 7.2

Thought ntfs-3g, keeps appearing in process list, praise God as of time of writting NTFS support on FreeBSD prooved to be stable.
Read / Write disk operations to the NTFS I tested it with works great. Just about 5 years ago I still remember write mode was still experimental. Now it seems NTFS mounts can be used with no hassle even on production machines.

4. Auto mounting NTFS partition on FreeBSD system boot

There are two approaches towards 'the problem' I can think of.
The better way to auto mount on boot (in my view) is through /etc/fstab use

If /etc/fstab + ntfs-3g is to be used, you will however change the default /sbin/mount_ntfs command to point to /usr/local/bin/ntfs-3g, i.e.:

freebsd# mv /sbin/mount_ntfs /sbin/mount_ntfs.orig
freebsd# ln -s /usr/local/bin/ntfs-3g /sbin/mount_ntfs

Then to mount /dev/da0s1 via /etc/fstab add line:

/dev/ad0s1 /mnt/disk ntfs rw,late 0 0

To not bother with text editor run:

freebsd# echo '/dev/ad0s1 /mnt/disk ntfs rw,late 0 0' >> /etc/fstab

I've red in posts in freebsd forums, there is also a way to use ntfs-3g for mounting partitions, without substituting the original bsd /sbin/mount_ntfs, the exact commands suggested to be used with no need to prior mv /sbin/mount_ntfs to /sbin/mount_ntfs.orig and link it to ntfs is:

/dev/ad0s1 /disk ntfs rw,mountprog=/usr/local/bin/ntfs-3g,late 0 0

For any other NTFS partitions, for instance /dev/ad0s2, /dev/ad2s1 etc. simply change the parititon name and mount points.

The second alternative to adding the NTFS to auto mount is through /etc/rc.local. /etc/rc.local content will be executed very late in system boot. :

echo '/usr/local/bin/ntfs-3g -o rw /dev/da0s1' >> /etc/rc.local

One disadvanage of using /etc/rc.local for mounting the partition is the hanging ntfs-3g in proc list:

freebsd# ps ax |grep -i ntfs|grep -v grep
18892 ?? Is 0:00.00 /usr/local/bin/ntfs-3g -o rw /dev/da0s1 /mnt/disk/

Though, I haven't tested it yet. Using the same methodology should be perfectly working on PC-BSD, DragonFlyBSD, NetBSD and OpenBSD.
I will be glad if someone who runs any of the other BSDs can confirm, following this instructions works fine on these BSDs too.

How to solve “Incorrect key file for table ‘/tmp/#sql_9315.MYI’; try to repair it” mysql start up error

Saturday, April 28th, 2012

When a server hard disk scape gets filled its common that Apache returns empty (no content) pages…
This just happened in one server I administer. To restore the normal server operation I freed some space by deleting old obsolete backups.
Actually the whole reasons for this mess was an enormous backup files, which on the last monthly backup overfilled the disk empty space.

Though, I freed about 400GB of space on the the root filesystem and on a first glimpse the system had plenty of free hard drive space, still restarting the MySQL server refused to start up properly and spit error:

Incorrect key file for table '/tmp/#sql_9315.MYI'; try to repair it" mysql start up error

Besides that there have been corrupted (crashed) tables, which reported next to above error.
Checking in /tmp/#sql_9315.MYI, I couldn't see any MYI – (MyISAM) format file. A quick google look up revealed that this error is caused by not enough disk space. This was puzzling as I can see both /var and / partitions had plenty of space so this shouldn't be a problem. Also manally creating the file /tmp/#sql_9315.MYI with:

server:~# touch /tmp/#sql_9315.MYI

Didn't help it, though the file created fine. Anyways a bit of a closer examination I've noticed a /tmp filesystem mounted besides with the other file system mounts ????
You can guess my great amazement to find this 1 Megabyte only /tmp filesystem hanging on the server mounted on the server.

I didn't mounted this 1 Megabyte filesystem, so it was either an intruder or some kind of "weird" bug…
I digged in Googling to see, if I can find more on the error and found actually the whole mess with this 1 mb mounted /tmp partition is caused by, just recently introduced Debian init script /etc/init.d/mountoverflowtmp.
It seems this script was introduced in Debian newer releases. mountoverflowtmp is some kind of emergency script, which is triggered in case if the root filesystem/ space gets filled.
The script has only two options:

# /etc/init.d/mountoverflowtmp
Usage: mountoverflowtmp [start|stop]

Once started what it does it remounts the /tmp to be 1 megabyte in size and stops its execution like it never run. Well maybe, the developers had something in mind with introducing this script I will not argue. What I should complain though is the script design is completely broken. Once the script gets "activated" and does its job. This 1MB mount stays like this, even if hard disk space is freed on the root partition – / ….

Hence to cope with this unhandy situation, once I had freed disk space on the root partition for some reason mountoverflowtmp stop option was not working,
So I had to initiate "hard" unmount:

server:~# mount -l /tmp

Also as I had a bunch of crashed tables and to fix them, also issued on each of the broken tables reported on /etc/init.d/mysql start start-up.

server:~# mysql -u root -p
mysql> use Database_Name;
mysql> repair table Table_Name extended;
....

Then to finally solve the stupid Incorrect key file for table '/tmp/#sql_XXYYZZ33444.MYI'; try to repair it error, I had to restart once again the SQL server:

Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld.
Checking for corrupt, not cleanly closed and upgrade needing tables..
root@server:/etc/init.d#

Tadadadadam!, SQL now loads and works back as before!

How to check /dev/ partition disk labeling in Debian GNU / Linux

Thursday, December 8th, 2011

The usual way that one is supposed to check a certain partition let’s say /dev/sda1 disk UUID (Universal Unique Identifier) label is through a command:
vol_id /dev/sda1

For reason however Debian does not include vol_id command. To check the UUID assigned disk labels on Debian one should use another command called blkid (part of util-linux deb package).

blkid will list all block device attributes so it doesn’t specifically, passing any partition as argument.
Here is an example output of blkid :

server:/root# blkid
/dev/sda1: UUID="cdb1836e-b7a2-4cc7-b666-8d2aa31b2da4" SEC_TYPE="ext2" TYPE="ext3"
/dev/sda5: UUID="c67d6d43-a48f-43ff-9d65-7c707a57dfe6" TYPE="swap"
/dev/sdb1: UUID="e324ec28-cf04-4e2e-8953-b6a8e6482425" TYPE="ext2"
/dev/sdb5: UUID="1DWe0F-Of9d-Sl1J-8pXW-PLpy-Wf9s-SsyZfQ" TYPE="LVM2_member"
/dev/mapper/computer-root: UUID="fbdfc19e-6ec8-4000-af8a-cde62926e395" TYPE="ext3"
/dev/mapper/computer-swap_1: UUID="e69100ab-9ef4-45df-a6aa-886a981e5f26" TYPE="swap"
/dev/mapper/computer-home: UUID="2fe446da-242d-4cca-8b2c-d23c76fa27ec" TYPE="ext3"

 

How to check any filesystem for bad blocks using GNU / Linux or FreeBSD with dd

Monday, November 28th, 2011

Check any filesystem partition for BAD BLOCKS with DD on GNU Linux and FreeBSD

Have you looked for a universal physical check up tool to check up any filesystem type existing on your hard drive partitions?
I did! and was more than happy to just recently find out that the small UNIX program dd is capable to check any file system which is red by the Linux or *BSD kernel.

I’ll give an example, I have few partitions on my laptop computer with linux ext3 filesystem and NTFS partition.
My partitions looks like so:

noah:/home/hipo# fdisk -l
Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x2d92834c
Device Boot Start End Blocks Id System
/dev/sda1 1 721 5786624 27 Unknown
Partition 1 does not end on cylinder boundary.
/dev/sda2 * 721 9839 73237024 7 HPFS/NTFS
/dev/sda3 9839 19457 77263200 5 Extended
/dev/sda5 9839 12474 21167968+ 83 Linux
/dev/sda6 12474 16407 31593208+ 83 Linux
/dev/sda7 16407 16650 1950448+ 82 Linux swap / Solaris
/dev/sda8 16650 19457 22551448+ 83 Linux

For all those unfamiliar with dddd – convert and copy a file this tiny program is capable of copying data from (if) input file to an output file as in UNIX , the basic philosophy is that everything is a file partitions themselves are also files.
The most common use of dd is to make image copies of a partition with any type of filesystem on it and move it to another system
Looking from a Windows user perspective dd is the command line Norton Ghost equivalent for Linux and BSD systems.
The classic way dd is used to copy let’s say my /dev/sda1 partition to another hard drive /dev/hdc1 is by cmds:

noah:/home/hipo# dd if=/dev/sda1 of=/dev/hdc1 bs=16065b

Even though the basic use of dd is to copy files, its flexibility allows a “trick” through which dd can be used to check any partition readable by the operating system kernel for bad blocks

In order to check any of the partitions listed, let’s say the one listed with filesystem HPFS/NTFS on /dev/sda2 using dd

noah:/home/hipo# dd if=/dev/sda2 of=/dev/null bs=1M

As you can see the of (output file) for dd is set to /dev/null in order to prevent dd to write out any output red by /dev/sda2 partition. bs=1M instructs dd to read from /dev/sda2 by chunks of 1 Megabyte in order to accelerate the speed of checking the whole drive.
Decreasing the bs=1M to less will take more time but will make the bad block checking be more precise.
Anyhow in most cases bs of 1 Megabyte will be a good value.

After some minutes (depending on the partition size), dd if, of operations outputs a statistics informing on how dd operations went.
Hence ff some of the blocks on the partition failed to be red by dd this will be shown in the final stats on its operation completion.
The drive, I’m checking does not have any bad blocks and dd statistics for my checked partition does not show any hard drive bad block problems:

71520+1 records in
71520+1 records out
74994712576 bytes (75 GB) copied, 1964.75 s, 38.2 MB/s

The statistics is quite self explanatory my partition of s size 75 GB was scanned for 1964 seconds roughly 32 minutes 46 seconds. The number of records red and written are 71520+1 e.g. (records in / records out). This means that all the records were properly red and wrote to /dev/null and therefore no BAD blocks on my NTFS partition 😉

How to debug mod_rewrite .htaccess problems with RewriteLog / Solve mod_rewrite broken redirects

Friday, September 30th, 2011

Its common thing that CMS systems and many developers custom .htaccess cause issues where websites depending on mod_rewrite fails to work properly. Most common issues are broken redirects or mod_rewrite rules, which behave differently among the different mod_rewrite versions which comes with different versions of Apache.

Everytime there are such problems its necessery that mod_rewrite’s RewriteLog functionality is used.
Even though the RewriteLog mod_rewrite config variable is well described on httpd.apache.org , I decided to drop a little post here as I’m pretty sure many novice admins might not know about RewriteLog config var and might benefit of this small article.
Enabling mod_rewrite requests logging of requests to the webserver and process via mod_rewrite rules is being done either via the specific website .htaccess (located in the site’s root directory) or via httpd.conf, apache2.conf etc. depending on the Linux / BSD linux distribution Apache config file naming is used.

To enable RewriteLog near the end of the Apache configuration file its necessery to place the variables in apache conf:

1. Edit RewriteLog and place following variables:

RewriteLogLevel 9
RewriteLog /var/log/rewrite.log

RewriteLogLevel does define the level of logging that should get logged in /var/log/rewrite.log
The higher the RewriteLogLevel number defined the more debugging related to mod_rewrite requests processing gets logged.
RewriteLogLevel 9 is actually the highest loglevel that can be. Setting the RewriteLogLevel to 0 will instruct mod_rewrite to stop logging. In many cases a RewriteLogLevel of 3 is also enough to debug most of the redirect issues, however I prefer to see more, so almost always I use RewriteLogLevel of 9.

2. Create /var/log/rewrite.log and set writtable permissions

a. Create /var/log/rewrite.log

freebsd# touch /var/log/rewrite.log

b. Set writtable permissons

Either chown the file to the user with which the Apache server is running, or chmod it to permissions of 777.

On FreeBSD, chown permissions to allow webserver to write in file, should be:

freebsd# chown www:www /var/log/rewrite.log

On Debian and alike distros:

debian:~# chown www-data:www-data /var/log/rewrite.log

On CentOS, Fedora etc.:

[root@centos ~]# chown httpd:httpd /var/log/rewrite.log

On any other distribution, you don’t want to bother to check the uid:gid, the permissions can be set with chmod 777, e.g.:

linux# chmod 777 /var/log/rewrite.log

Next after RewriteLog is in conf to make configs active the usual webserver restart is required.

To restart Apache On FreeBSD:

freebsd# /usr/local/etc/rc.d/apache2 restart
...

To restart Apache on Debian and derivatives:

debian:~# /etc/init.d/apache2 restart
...

On Fedora and derivive distros:

[root@fedora ~]# /etc/init.d/httpd restart
...

Its common error to forget to set proper permissions to /var/log/rewrite.log this has puzzled me many times, when enabling RewriteLog’s logging.

Another important note is when debugging for mod_rewrite is enabled, one forgets to disable logging and after a while if the /var/log partition is placed on a small partition or is on an old server with less space often the RewriteLog fills in the disk quickly and might create website downtimes. Hence always make sure RewriteLog is disabled after work rewrite debugging is no longer needed.

The way I use to disable it is by commenting it in conf like so:

#RewriteLogLevel 9
#RewriteLog /var/log/rewrite.log

Finally to check, what the mod_rewrite processor is doing on the fly its handy to use the well known tail -f

linux# tail -f /var/log/rewrite.log

A bunch of time in watching the requests, should be enough to point to the exact problem causing broken redirects or general website malfunction.
Cheers 😉

How to enable AUTO fsck (ext3, ext4, reiserfs, LVM filesystems) checking on Linux boot through /etc/fstab

Tuesday, July 12th, 2011

How to auto FSCK manual fsck screenshot

Are you an administrator of servers and it happens a server is DOWN.
You request the Data Center to reboot, however suddenly the server fails to boot properly and you have to request for IPKVM or some web java interface to directly access the server physical terminal …

This is a very normal admin scenario and many people who have worked in the field of remote system administrators (like me), should have experienced that bad times multiple times.

Sadly enough only a insignifant number of administrators try to do their best to reduce this down times to resolve client stuff downtime but prefer spending time playing the ztype! game or watching some porn website 😉

Anyways there are plenty of things like Server Auto Reboot on Crash with software Watchdog etc., that we as sysadmins can do to reduce server downtimes and most of the manual human interactions on server boot time.

In that manner of thougts a very common thing when setting up a new Linux server that many server admins forget or don’t know is to enable all the server partition filesystems to be auto fscked during server boot time.

By not enabling the auto filesystem check options in Linux the server filesystems did not automatically scan and fix hard drive partitions for fs innode inconsistencies.
Even though the filesystems are tuned to automatically get checked on every 38 system reboots, still if some kind of filesystem errors are found that require a manual confirmation the boot process is interrupted and the admin ends up with a server which is not reachable remotely via ssh !

For the remote system administrator, this times are a terrible times of waitings, prayers and hopes that the server hardware is fine 😉 as well as being on hold to get a KVM to get into the server manually and enter the necessery input to fsck prompt.

Many of this bad times can be completely avoided with a very simple fix through /etc/fstab by enabling all server partitions containing any filesystem to be automatically checked and fixed in case if inconsistencies or errors are found by fsck.ext3, fsck.ext4, fsck.reiserfs etc. commands.

A very typical default /etc/fstab file you will find on many servers should look something like:

/dev/sda8 / ext3 errors=remount-ro 0 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/sda1 /home ext3 defaults 0 0

Notice the line:
/dev/sda1 /home ext3 defaults 0 0

The first column in the example contains the device name, the second one its mount point, third its filesystem type, fourth the mount options, fifth (a number) dump options, and sixth (another number) filesystem check options. Let’s take a closer look at this stuff.

The ones which are interesting to enable auto fsck checking and error resolving is provided usually by the last sixth variable (filesystem check option) which in the above example equals 0 .

When the filesystem check option equals 0 this means the auto fsck and repair for the respective filesystem is disabled.
Some time in the past the dump backup option (5th option in the example) was also used but as far as I can understand today it’s not that important in modern GNU/Linux distributions.

Now having the above sample crontab in order to enable the fsck file checking on Linux boot for /dev/sda1 , we will need to modify the above line’s filesystem check option be 2, e.g. the line would afterwards look like:

/dev/sda1 /home ext3 defaults 0 2

Setting the 2 as an option for filesystem check is necessery for every filesystem which is not mounted as a root filesystem /

In above example /etc/fstab you already see that auto filesystem fsck is enabled for root partition:

/dev/sda8 / ext3 errors=remount-ro 0 1
(notice the 1 in the end of the line)

Finally a modified version of the default sample /etc/fstab which will check the extra /dev/sda1 /home partition would look like so:

/dev/sda8 / ext3 errors=remount-ro 0 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/sda1 /home ext3 defaults 0 2

Making sure all Linux server partitions has the auto filesystem check option enabled is something absoultely necessery!
Enabling the auto fsck on servers always makes me sleep calmer 😉
Hope it helps your too. 🙂