Relabel a FAT File System in Linux

The venerable fat16 and fat32 file systems are still in widespread use today. Devices such as digital cameras, satellite navigation systems, memory sticks and mp3 players all make use of FAT

Mount a FAT file system in Linux, and it will appear as something like this:

[root@pluto ~]# df
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/sdb         7716112   7274796    441316  95% /media/0EB5-6037
/dev/sdc1       15549952  14225152   1324800  92% /media/1FC3-3137

Those hex numbers on the left are the default volume labels, and pretty unfriendly they are. The two entries above actually correspond to an MP3 player (Sansa Clip+) and the player’s expansion SD card. I used mlable to allocate more meaningful volume names. Continue reading

Format and Relabel a Flash Drive in Linux

Flash drives (as in memory sticks) are a popular choice for backups. A 64 Gb drive can be bought for just over £20 at the time of writing. Once your data is backed up to the drive, it is easy to store in a safe place or transport off site for added protection. Actually that applies to any portable hard drive, as does the following procedure.

Most flash drives come formatted as FAT32. That is fine from day-to-day but there is a strict 4 GB limit applying to the size of any file. Backup software is likely to produce large archive files well over 4 GB, so won’t work well with FAT32. What’s needed therefore, is a better file system. Continue reading

Large Directory Causes ls to "Hang"

So you have a directory with millions of files, and ls just hangs ?

Use ls -1 -f to show the files immediately. To delete the files, if you want to remove ALL files in the current directory, use something like

ls -1 -f | xargs rm

After cleaning up very many unwanted files, you are likely to be left with a huge and sparse directory object. Three million files in one directory, for example, apart from taking up space in themselves, will likely push the directory object to occupy over 100 Mb of space. Continue reading

Large files / small backups on Debian LAMP

Backups on a LAMP server were much smaller than expected, and the cause was excessively large log files. This post explains the apparent paradox and the steps taken to trace and fix the problem.

The server in question runs the usual set of grandfather-father-son backups. Before each backup, the software prints the expected size of the backup into a log file. On other servers the estimate is usually bang-on. On this server, the backup turned out to be about 12 times smaller than the estimate. Not a problem in itself, but puzzling and indicative of something untoward on the system. Continue reading

ZFS Corruption Persists in Unlinked Files

This article explains how zfs errors can sometimes persist even after the files containing the offending blocks have been deleted, and presents an easy way of removing corruption.

Most solaris sysadmins will be familiar with the following situation. A zpool gives errors about failed checksums and enters a degraded state: Continue reading

Fedora Dual Boot Convoluted Boot Path

This post describes a problem with receiving Linux kernel updates after installing Fedora 16 in a dual boot environment. The Fedora installation process allows the user to rewrite Grub in the master boot record (MBR) or to leave the MBR untouched. I chose to leave it untouched, leading to a later kernel update problem which was fairly easily solved with some Grub 2 commands. Continue reading

HP-UX fasdm fails with vx_nospace

HP-UX file systems can be extended with a combination of the lvextend and fsadm commands. It’s well known procedure that has been in widespread use for several years, allowing online file system extensions, ie. the file system can be extended while it is mounted and busy. The file system type must be of type “vxfs” and enclosed in an LVM logical volume.

Occasional difficulties can occur if the file system is 100% full. I recently encountered the following vx_nospace error when trying to extend a file system from 9 Gb to 59 Gb under HP-UX 11.31. Continue reading

Sorting a Directory in the FAT File System

The venerable fat16 and fat32 file systems are still in widespread use today. Devices such as digital cameras, satellite navigation systems, memory sticks and mp3 players all make use of FAT.

The files in a FAT file system are arranged in a strict order. This can affect the way that some devices behave. For example, some MP3 players will play songs only in the order in which they are arranged on the device, rather than the more convenient alphabetical or alphanumeric order. Music players that use USB memory sticks and in-car USB systems can be affected in the same way. The only way to get the songs to play in a more sensible order is to sort the directory (folder) in which they are located. Continue reading

Solaris Disk EFI Headers

“format” is the Solaris tool used to initialize disks. Format can sometimes have a problem with disks that bear an EFI disk label. In which case, replacing the EFI label with a more traditional VTOC disk label can help.

The problem appears when an attempt is made to label the disk using format. The label operation fails with “Current disk is unformatted”. Many other format options fail with the same message. Newfs will not recognise the disk and it is therefore impossible to create a file system. Continue reading

Copying Directories with SSH

Copying data is something every administrator does.  A single file or directory file can be copied with a single command.  Moving information from one system to another needs a bit more work, but it needn’t be a pain.

The ssh command can be used to copy data from one Unix system to another.    Here is an example for HP-UX, but it works on Linux too.  A directory, called /var/opt/ignite, is copied from the system “pluto” to another machine called “jupiter”. Continue reading