bash « blog.yo61.com

When you install an update to a package on an RPM-based system, any configuration files which were originally distributed by the package and that have been changed are not replaced when the package is updated. Instead, rpm creates a new file with the extention ".rpmnew". It is then necessary to manually compare the existing file and the new one and decide how to deal with the new file.

So, the pattern I often need to use is "list all .rpmnew files and the corresponding original file". This is not a particularly complex issue, but is one that I don't use often enough to have at my fingertips. The trick is bash variable substitution; specifically pattern matching: ${variable%pattern}. This deletes the shortest possible match for pattern from the right of the contents of $variable.

An example using .rpmnew files created when upgading OpenNMS:

# ls -1 *.rpmnew| while read f ; do ls -l ${f%\.rpmnew}* ; done -rw-rw-r-- 1 root root 7285 Jun 3 12:43 database-reports.xml -rw-rw-r-- 1 root root 8232 Aug 10 19:01 database-reports.xml.rpmnew -rw-rw-r-- 1 root root 333092 Aug 25 09:25 datacollection-config.xml -rw-rw-r-- 1 root root 314141 May 11 01:31 datacollection-config.xml.rpmnew -rw-rw-r-- 1 root root 3395 Jun 3 12:43 jasper-reports.xml -rw-rw-r-- 1 root root 3664 Aug 10 19:01 jasper-reports.xml.rpmnew -rw-rw-r-- 1 root root 25887 Aug 10 19:01 log4j.properties -rw-rw-r-- 1 root root 25887 May 11 01:31 log4j.properties.rpmnew -rw-rw-r-- 1 root root 19319 Apr 22 16:56 opennms.properties -rw-rw-r-- 1 root root 19635 Aug 10 19:01 opennms.properties.rpmnew -rw-rw-r-- 1 root root 9252 Apr 22 16:59 rrd-configuration.properties -rw-rw-r-- 1 root root 9604 May 11 01:31 rrd-configuration.properties.rpmnew -rw-r--r-- 1 root root 669444 Jun 3 13:51 snmp-graph.properties -rw-rw-r-- 1 root root 604457 Aug 10 19:01 snmp-graph.properties.rpmnew

Some kind soul on #bash on Freenode recently pointed me at this excellent document:

http://mywiki.wooledge.org/BashPitfalls

(I ran into #20, in case you're wondering)

I needed to check the integrity of the file systems on several xen domU guests while the guests were shutdown, ie. I needed to do it from the dom0.

I use LVM logical volumes for the block devices for the guests disks named $host-disk0. These are stored in a volume group named vg_guests. I use kpartx to access the partitions on the block device.

Each guest disk has a small physical partition for /boot; the rest of the disk is allocated to a 2nd partition which is used as an LVM volume group named vg_$host.

Here's a script I knocked up to do the job:

for host in host1 host2 host3 ; do
    # create devices from the LVs
    kpartx -av /dev/mapper/vg_guests-$host--disk*
 
    # Activate the VGs for the host
    for vg in $(vgs --noheadings | grep $host | awk &#39;{print $1}&#39; ) ; do
        echo Activating $vg
        vgchange -ay $vg
    done
 
    # check the file systems
    for p in $(/dev/mapper/vg_$host* | grep -v swap); do
        e2fsck -p $p
    done
 
    # Deactivate the VGs
    for vg in $(vgs --noheadings | grep $host | awk &#39;{print $1}&#39; ) ; do
        echo De-activating $vg
        vgchange -an $vg
    done
 
    # Remove the devices
    kpartx -dv /dev/mapper/vg_guests-$host--disk0
done

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Tag Archives: bash

Listing all files with their .rpmnew updates

Bash pitfalls

Check file system integrity of multiple xen domU guests