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Category Archives: Linux

Flushing nscd’s cache

22-Dec-09

By default, in RHEL, nscd is configured to have a persistent cache – one that is “stored on the disk and therefore survive[s] a nscd restart or e.g. machine reboot” according to the nscd.conf man page.
To flush the cache, you must run nscd with the “-i” flag instead of simply restarting it:

sudo [...]

Creating an XFS Partition

23-Jun-09

Steps for creating an XFS partition on /dev/sdc which encompasses the entire disk. (LVM is not used in this example. Post written using Scientific Linux 5.3, but should be relevant to any RHEL clone with XFS support.)
Partition the disk using fdisk; we want the standard Linux partition id of “83″, so no need [...]

Extracting an RPM without installing it

01-Apr-09

If you want to inspect files in an RPM without installing it, use rpm2cpio piped to cpio:
rpm2cpio file.rpm | cpio -id
Note that this will create a (local) directory tree under which the extracted files will be placed. In other words, expect the files to be extracted under a newly created “usr” directory or similar.

Access control lists on Linux

15-Jan-09

To view ACLs on a file:
> getfacl file.txt
To modify the ACL on a file:
> setfacl -m user:rwx file.txt
To recursively change an ACL:
> setfacl -R -m user:rwx .
To modify the default ACL for a directory:
> setfacl -d -m user:rwx.
See the getfacl and setfacl man pages for more information.

Displaying Boot Messages on Ubuntu

06-Jan-09

To display Ubuntu boot messages one time, do the following:

Press “e” while the GRUB screen to select a kernel version is displayed.
Edit the kernel line, again by pressing “e”, to remove any references to “quiet” – it is generally at the end of the line, with “splash”.
Edit the fifth line, below the “initrd” line – [...]

Fixing RPM Database Errors After an Upgrade of the RPM Package

28-Dec-08

For errors similar to these:
rpmdb: Program version 4.2 doesn’t match environment version
error: db4 error(22) from dbenv->open: Invalid argument
error: cannot open Packages index using db3 – Invalid argument (22)
error: cannot open Packages database in /var/lib/rpm
Do this:
# rm -f /var/lib/rpm/__*