TOPIC: FILE SYSTEM
A Practical Linux Administration Toolkit: Kernels, Storage, Filesystems, Transfers and Shell Completion
4th February 2026
Linux command-line administration has a way of beginning with a deceptively simple question that opens into several possible answers. Whether the task is checking which kernels are installed before an upgrade, mounting an NFS share for backup access, diagnosing low disk space, throttling a long-running sync job or wiring up tab completion, the right answer depends on context: the distribution, the file system type, the transport protocol and whether the need is a one-off action or a persistent configuration. This guide draws those everyday administrative themes into a single continuous reference.
Identifying Your System and Installed Kernels
Reading Distribution Information
A sensible place to begin any administration session is knowing exactly what you are working with. One quick approach is to read the release files directly:
cat /etc/*-releaseOn systems where bat is available (sometimes installed as batcat), the same files can be read with syntax highlighting using batcat /etc/*-release. Typical output on Ubuntu includes /etc/lsb-release and /etc/os-release, with values such as DISTRIB_ID=Ubuntu, VERSION_ID="20.04" and PRETTY_NAME="Ubuntu 20.04.6 LTS". Three additional commands, cat /etc/os-release, lsb_release -a and hostnamectl, each present the same underlying facts in slightly different formats, while uname -r reports the currently running kernel release in isolation. Adding more flags with uname -mrs extends the output to include the kernel name and machine hardware class, which on an older RHEL system might return something like Linux 2.6.18-8.1.14.el5 x86_64.
Querying Installed Kernels by Package Manager
On Red Hat Enterprise Linux, CentOS, Rocky Linux, AlmaLinux, Oracle Linux and Fedora, installed kernels are managed by the RPM package database and are queried with:
rpm -qa kernelThis may return entries such as kernel-5.14.0-70.30.1.el9_0.x86_64. The same information is also accessible through yum list installed kernel or dnf list installed kernel. On Debian, Ubuntu, Linux Mint and Pop!_OS the package manager differs, so the command changes accordingly:
dpkg --list | grep linux-imageOutput may include versioned packages, such as linux-image-2.6.20-15-generic, alongside the metapackage linux-image-generic. Arch Linux users can query with pacman -Q | grep linux, while SUSE Enterprise Linux and openSUSE users can turn to rpm -qa | grep -i kernel or use zypper search -i kernel, which presents results in a structured table. Alpine Linux takes yet another approach with apk info -vvv | grep -E 'Linux' | grep -iE 'lts|virt', which may return entries such as linux-virt-5.15.98-r0 - Linux lts kernel.
Finding Kernels Outside the Package Manager
Package databases do not always tell the whole story, particularly where custom-compiled kernels are involved. A kernel built and installed manually will not appear in any package manager query at all. In that case, /lib/modules/ is a useful place to look, since each installed kernel generally has a corresponding module directory. Running ls -l /lib/modules/ may show entries such as 4.15.0-55-generic, 4.18.0-25-generic and 5.0.0-23-generic. A further check is:
sudo find /boot/ -iname "vmlinuz*"This may return files such as /boot/vmlinuz-5.4.0-65-generic and /boot/vmlinuz-5.4.0-66-generic, confirming precisely which versions exist on disk.
A Brief History of vmlinuz
That naming convention is worth understanding because it appears on virtually every Linux system. vmlinuz is the compressed, bootable Linux kernel image stored in /boot/. The name traces back through computing history: early Unix kernels were simply called /unix, but when the University of California, Berkeley ported Unix to the VAX architecture in 1979 and added paged virtual memory, the resulting system, 3BSD, was known as VMUNIX (Virtual Memory Unix) and its kernel images were named /vmunix. Linux inherited vmlinuz as a mutation of vmunix, with the trailing z denoting gzip compression (though other algorithms such as xz and lzma are also supported). The counterpart vmlinux refers to the uncompressed, non-bootable kernel file, which is used for debugging and symbol table generation but is not loaded directly at boot. Running ls -l /boot/ will show the full set of boot files present on any given system.
Examining and Investigating Disk Usage
Why ls Is Not the Right Tool for Directory Sizes
Storage management is an area where a familiar command can mislead. Running ls -l on a directory typically shows it occupying 4,096 bytes, which reflects the directory entry metadata rather than the combined size of its contents. For real space consumption, du is the appropriate tool.
sudo du -sh /varThe above command produces a summarised, human-readable total such as 85G /var. The -s flag limits output to a single grand total and -h formats values in K, M or G units. For an individual file, du -sh /var/log/syslog might report 12M /var/log/syslog, while ls -lh /var/log/syslog adds ownership and timestamps to the same figure.
Drilling Down to Find Where Space Has Gone
When a file system is full and the need is to locate exactly where the space has accumulated, du can be made progressively more revealing. The command sudo du -h --max-depth=1 /var lists first-level subdirectories with sizes, potentially showing 77G /var/lib, 5.0G /var/cache and 3.3G /var/log. To surface the biggest consumers quickly, piping to sort and head works well:
sudo du -h /var/ | sort -rh | head -10Adding the -a flag includes individual files alongside directories in the same output:
sudo du -ah /var/ | sort -rh | head -10Apparent Size Versus Allocated Disk Space
There is a subtle distinction that sometimes causes confusion. By default, du reports allocated disk usage, which is governed by the file system block size. A single-byte file on a file system with 4 KB blocks still consumes 4 KB of disk. To see the amount of data actually stored rather than allocated, sudo du -sh --apparent-size /var reports the apparent size instead. The df command answers a different question altogether: it shows free and used space per mounted file system, such as /dev/sda1 at 73 per cent usage or /dev/sdb1 mounted on /data with 70 GB free. In practice, du is for locating what consumes space and df is for checking how much remains on each volume.
gdu: A Faster Interactive Alternative
Some administrators prefer a more modern tool for storage investigations, and gdu is a notable option. It is a fast disk usage analyser written in Go with an interactive console interface, designed primarily for SSDs where it can exploit parallel processing to full effect, though it functions on hard drives too with less dramatic speed gains. The binary release can be installed by extracting its .tgz archive:
curl -L https://github.com/dundee/gdu/releases/latest/download/gdu_linux_amd64.tgz | tar xz
chmod +x gdu_linux_amd64
mv gdu_linux_amd64 /usr/bin/gduIt can also be run directly via Docker without installation:
docker run --rm --init --interactive --tty --privileged
--volume /:/mnt/root ghcr.io/dundee/gdu /mnt/rootIn use, gdu scans a directory interactively when run without flags, summarises a target with gdu -ps /some/dir, shows top results with gdu -t 10 / and runs without interaction using gdu -n /. It supports apparent size display, hidden file inclusion, item counts, modification times, exclusions, age filtering and database-backed analysis through SQLite or BadgerDB. The project documentation notes that hard links are counted only once and that analysis data can be exported as JSON for later review.
Unpacking TGZ Archives
A brief note on the tar command is useful here, since it appears throughout Linux administration, including in the gdu installation step above. A .tgz file is simply a GZIP-compressed tar archive, and the standard way to extract one is:
tar zxvf archive.tgzModern GNU tar can detect the compression type automatically, so the -z flag is often optional:
tar xvf archive.tgzTo extract into a specific directory rather than the current working directory, the -C option takes a destination path:
tar zxvf archive.tgz -C /path/to/destination/To inspect the contents of a .tgz file without extracting it, the t (list) flag replaces x (extract):
tar ztvf archive.tgzThe tar command was first introduced in the seventh edition of Unix in January 1979 and its name comes from its original purpose as a Tape ARchiver. Despite that origin, modern tar reads from and writes to files, pipes and remote devices with equal facility.
Mounting NFS Shares and Optical Media
Installing NFS Client Tools
NFS remains common on Linux and Unix-like systems, allowing remote directories to be mounted locally and treated as though they were native file systems. Before a client can mount an NFS export, the client packages must be installed. On Ubuntu and Debian, that means:
sudo apt update
sudo apt install nfs-commonOn Fedora and RHEL-based distributions, the equivalent is:
sudo dnf install nfs-utilsOnce installed, showmount -e 10.10.0.10 can list available exports from a server, returning output such as /backups 10.10.0.0/24 and /data *.
Mounting an NFS Share Manually
Mounting an NFS share follows the same broad pattern as mounting any other file system. First, create a local mount point:
sudo mkdir -p /var/backupsThen mount the remote export, specifying the file system type explicitly:
sudo mount -t nfs 10.10.0.10:/backups /var/backupsA successful command produces no output. Verification is done with mount | grep nfs or df -h, after which the local directory acts as the root of the remote file system for all practical purposes.
Persisting NFS Mounts Across Reboots
Since a manual mount does not survive a reboot, persistent setups use /etc/fstab. An appropriate entry looks like:
10.10.0.10:/backups /var/backups nfs defaults,nofail,_netdev 0 0The nofail option prevents a boot failure if the NFS server is unavailable when the machine starts. The _netdev flag marks the mount as network-dependent, ensuring the system defers the operation until the network stack is available. Running sudo mount -a tests the entry without rebooting.
Troubleshooting Common NFS Errors
NFS problems are often predictable. A "Permission denied" error usually means the server export in /etc/exports does not include the client, and reloading exports with sudo exportfs -ar is frequently the remedy. "RPC: Program not registered" indicates the NFS service is not running on the server, in which case sudo systemctl restart nfs-server applies. A "Stale file handle" error generally follows a server reboot or a deleted file and is cleared by unmounting and remounting. Timeouts and "Server not responding" messages call for checking network connectivity, confirming that firewall rules permit access to port 111 (rpcbind, required for NFSv3) and port 2049 (NFS itself), and verifying NFS version compatibility using the vers=3 or vers=4 mount option. NFSv4 requires only port 2049, while NFSv2 and NFSv3 also require port 111. To detach a share, sudo umount /var/backups is the standard route, with fuser -m /var/backups helping identify processes that are blocking the unmounting process.
Mounting Optical Media
CDs and DVDs are less central than they once were, but some systems still need to read them. After inserting a disc, blkid can identify the block device path, which is typically /dev/sr0, and will report the file system type as iso9660. With a mount point created using sudo mkdir /mnt/cdrom, the disc is mounted with:
sudo mount /dev/sr0 /mnt/cdromThe warning device write-protected, mounted read-only is expected for optical media and can be disregarded. CDs and DVDs use the ISO 9660 file system, a data-exchange standard designed to be readable across operating systems. Once mounted, the disc contents are accessible under /mnt/cdrom, and sudo umount /mnt/cdrom detaches it cleanly when work is complete.
Transferring Files Securely and Efficiently
Copying Files with scp
scp (Secure Copy) transfers files and directories between hosts over SSH, encrypting both data and authentication credentials in transit. Its basic syntax is:
scp [OPTIONS] [[user@]host:]source [[user@]host:]destinationThe colon is how scp distinguishes between local and remote paths: a path without a colon is local. A typical upload from a local machine to a remote host looks like:
scp file.txt remote_username@10.10.0.2:/remote/directoryA download from a remote host to the local machine reverses the argument order:
scp remote_username@10.10.0.2:/remote/file.txt /local/directoryCommonly used options include -r for recursive directory copies, -p to preserve metadata such as modification times and permissions, -C for compression, -i for a specific private key, -l to cap bandwidth in Kbit/s and the uppercase -P to specify a non-standard SSH port. It is also possible to copy between two remote hosts directly, routing the transfer through the local machine with the -3 flag.
The Protocol Change in OpenSSH 9.0
There is an important change in modern OpenSSH that administrators should be aware of. From OpenSSH 9.0 onward, the scp command uses the SFTP protocol internally by default rather than the older SCP/RCP protocol, which is now considered outdated. The command behaves identically from the user's perspective, but if an older server requires the legacy protocol, the -O flag forces it. For advanced requirements such as resumable transfers or incremental directory synchronisation, rsync is generally the better fit, particularly for large directory trees.
Throttling rsync to Protect Bandwidth
Even with rsync, raw speed is not always desirable. A backup script consuming all available bandwidth can disrupt other services on the same network link, so --bwlimit is often essential. The basic syntax is:
rsync --bwlimit=KBPS source destinationThe value is in units of 1,024 bytes unless an explicit suffix is added. A fractional value is also valid: --bwlimit=1.5m sets a cap of 1.5 MB/s. A local transfer capped at 1,000 KB/s looks like:
rsync --bwlimit=1000 /path/to/source /path/to/dest/And a remote backup:
rsync --bwlimit=1000 /var/www/html/ backups@server1.example.com:~/mysite.backups/The man page for rsync explains that --bwlimit works by limiting the size of the blocks rsync writes and then sleeping between writes to achieve the target average. Some volume undulation is therefore normal in practice.
Managing I/O Priority with ionice
Bandwidth is only one dimension of the load a transfer places on a system. Disk I/O scheduling may also need attention, particularly on busy servers running other workloads. The ionice utility adjusts the I/O scheduling class and priority of a process without altering its CPU priority. For instance:
/usr/bin/ionice -c2 -n7 rsync --bwlimit=1000 /path/to/source /path/to/dest/This runs the rsync process in best-effort I/O class (-c2) at the lowest priority level (-n7), combining transfer rate limiting with reduced I/O priority. The scheduling classes are: 0 (none), 1 (real-time), 2 (best-effort) and 3 (idle), with priority levels 0 to 7 available for the real-time and best-effort classes.
Together, --bwlimitand ionice provide complementary controls over exactly how much resource a routine transfer is permitted to consume at any given time.
Setting Up Bash Tab Completion
On Ubuntu and related distributions, Bash programmable completion is provided by the bash-completion package. If tab completion does not function as expected in a new installation or container environment, the following commands will install the necessary support:
sudo apt update
sudo apt upgrade
sudo apt install bash-completionThe package places a shell script at /etc/profile.d/bash_completion.sh. To ensure it is loaded in shell startup, the following appends the source line to .bashrc:
echo "source /etc/profile.d/bash_completion.sh" >> ~/.bashrcA conditional form avoids duplicating the line on repeated runs:
grep -wq '^source /etc/profile.d/bash_completion.sh' ~/.bashrc
|| echo 'source /etc/profile.d/bash_completion.sh' >> ~/.bashrcThe script is typically loaded automatically in a fresh login shell, but source /etc/profile.d/bash_completion.sh activates it immediately in the current session. Once active, pressing Tab after partial input such as sudo apt i or cat /etc/re completes commands and paths against what is actually installed. Bash also supports simple custom completions: complete -W 'google.com cyberciti.biz nixcraft.com' host teaches the shell to offer those three domains after typing host and pressing Tab, which illustrates how the feature can be extended to match the patterns of repeated daily work.
Installing Snap on Debian
Snap is a packaging format developed by Canonical that bundles an application together with all of its dependencies into a single self-contained package. Snaps update automatically, roll back gracefully on failure and are distributed through the Snap Store, which carries software from both Canonical and independent publishers. The background service that manages them, snapd, is pre-installed on Ubuntu but requires a manual setup step on Debian.
On Debian 9 (Stretch) and newer, snap can be installed directly from the command line:
sudo apt update
sudo apt install snapdAfter installation, logging out and back in again, or restarting the system, is necessary to ensure that snap's paths are updated correctly in the environment. Once that is done, install the snapd snap itself to obtain the latest version of the daemon:
sudo snap install snapdTo verify that the setup is working, the hello-world snap provides a straightforward test:
sudo snap install hello-world
hello-worldA successful run prints Hello World! to the terminal. Note that snap is not available on Debian versions before 9. If a snap installation produces an error such as snap "lxd" assumes unsupported features, the resolution is to ensure the core snap is present and current:
sudo snap install core
sudo snap refresh coreOn desktop systems, the Snap Store graphical application can then be installed with sudo snap install snap-store, providing a point-and-click interface for browsing and managing snaps alongside the command-line tools.
Increasing the Root Partition Size on Fedora with LVM
Fedora's default installer has used LVM (Logical Volume Manager) for many years, dividing the available disk into a volume group containing separate logical volumes for root (/), home (/home) and swap. This arrangement makes it straightforward to redistribute space between volumes without repartitioning the physical disk, which is a significant advantage over a fixed partition layout. Note that Fedora 33 and later default to Btrfs without LVM for new installations, so the steps below apply to systems that were installed with LVM, including pre-Fedora 33 installs and any system where LVM was selected manually.
Because the root file system is in active use while the system is running, resizing it safely requires booting from a Fedora Live USB stick rather than the installed system. Once booted from the live environment, open a terminal and begin by checking the volume group:
sudo vgsOutput such as the following shows the volume group name, total size and, crucially, how much free space (VFree) is unallocated:
VG #PV #LV #SN Attr VSize VFree
fedora 1 3 0 wz--n- <237.28g 0Before proceeding, confirm the exact device mapper paths for the root and home logical volumes by running fdisk -l, since the volume group name varies between installations. Common names include /dev/mapper/fedora-root and /dev/mapper/fedora-home, though some systems use fedora00 or another prefix.
When Free Space Is Already Available
If VFree shows unallocated space in the volume group, the root logical volume can be extended directly and the file system resized in a single command:
lvresize -L +5G --resizefs /dev/mapper/fedora-rootThe --resizefs flag instructs lvresize to resize the file system at the same time as the logical volume, removing the need to run resize2fs separately.
When There Is No Free Space
If VFree is zero, space must first be reclaimed from another logical volume before it can be given to root. The most common approach is to shrink the home logical volume, which typically holds the most available headroom. Shrinking a file system involves data moving on disk, so the operation requires the volume to be unmounted, which is why the live environment is essential. To take 10 GB from home:
lvresize -L -10G --resizefs /dev/mapper/fedora-homeOnce that completes, the freed space appears as VFree in vgs and can be added to the root volume:
lvresize -L +10G --resizefs /dev/mapper/fedora-rootBoth steps use --resizefs so that the file system boundaries are updated alongside the logical volume boundaries. After rebooting back into the installed system, df -h will confirm the new sizes are in effect.
Keeping a Linux System Well Maintained
The commands and configurations covered above form a coherent body of everyday Linux administration practice. Knowing where installed kernels are recorded, how to measure real disk usage rather than directory metadata, how to attach local and network file systems correctly, how to extract archives and move data securely without disrupting shared resources, how to make the shell itself more productive, how to extend a Debian system with snap packages and how to redistribute disk space between LVM volumes on Fedora converts a scattered collection of one-liners into a reliable working toolkit. Each topic interconnects naturally with the others: a kernel query clarifies what system you are managing, disk investigation reveals whether a file system has room for what you plan to transfer, NFS mounting determines where that transfer will land and bandwidth control determines what impact it will have while it runs.
Sorting out sluggish start-up and shutdown times in Linux Mint 19
9th August 2018
The Linux Mint team never forces users to upgrade to the latest version of their distribution, but curiosity often provides a strong enough impulse for me to do so. When I encounter rough edges, the wisdom of leaving things unchanged becomes apparent. Nevertheless, the process brings learning opportunities, which I am sharing in this post. It also allows me to collect various useful titbits that might help others.
Again, I went with the in-situ upgrade option, though the addition of the Timeshift backup tool means that it is less frowned upon than once would have been the case. It worked well too, apart from slow start-up and shutdown times, so I set about tracking down the causes on the two machines that I have running Linux Mint. As it happens, the cause was different on each machine.
On one PC, it was networking that holding up things. The cause was my specifying a fixed IP address in /etc/network/interfaces instead of using the Network Settings GUI tool. Resetting the configuration file back to its defaults and using the Cinnamon settings interface took away the delays. It was inspecting /var/log/boot.log that highlighted problem, so that is worth checking if I ever encounter slow start times again.
As I mentioned earlier, the second PC had a very different problem, though it also involved a configuration file. What had happened was that /etc/initramfs-tools/conf.d/resume contained the wrong UUID for my system's swap drive, so I was seeing messages like the following:
W: initramfs-tools configuration sets RESUME=UUID=<specified UUID for swap partition>
W: but no matching swap device is available.
I: The initramfs will attempt to resume from <specified file system location>
I: (UUID=<specified UUID for swap partition>)
I: Set the RESUME variable to override this.
Correcting the file and executing the following command resolved the issue by updating the affected initramfs image for all installed kernels and speeded up PC start-up times:
sudo update-initramfs -u -k all
Though it was not a cause of system sluggishness, I also sorted another message that I kept seeing during kernel updates and removals on both machines. This has been there for a while and causes warning messages about my system locale not being recognised. The problem has been described elsewhere as follows: /usr/share/initramfs-tools/hooks/root_locale is expecting to see individual locale directories in /usr/lib/locale, but locale-gen is configured to generate an archive file by default. Issuing the following command sorted that:
sudo locale-gen --purge --no-archive
Following these, my new Linux Mint 19 installations have stabilised with more speedy start-up and shutdown times. That allows me to look at what is on Flathub to see what applications and if they get updated to the latest version on an ongoing basis. That may be a topic for another entry on here, but the applications that I have tried work well so far.
Copying a directory tree on a Windows system using XCOPY and ROBOCOPY
17th September 2016
My usual method for copying a directory tree without any of the files in there involves the use of the Windows command line tool XCOPY and the command takes the following form:
xcopy /t /e <source> <destination>
The /t switch tells XCOPY to copy only the directory structure, while the /e one tells it to include empty directories too. Substituting /s for /e would ensure that only non-empty directories are copied. <source> and <destination> are the directory paths that you want to use and need to be enclosed in quotes if you have a space in a directory name.
There is one drawback to this approach that I have discovered. When you have long directory paths, messages about there being insufficient memory are issued and the command fails. The limitation has nothing to do with the machine that you are using, but is a limitation of XCOPY itself.
After discovering that, I got to check if ROBOCOPY can do the same thing without the same file path length limitation because I did not have the liberty of shortening folder names to get the whole path within the length expected by XCOPY. The following is the form of the command that I found did what I needed:
robocopy <source1> <destination1> /e /xf *.* /r:0 /w:0 /fft
Here, <source1> and <destination1> are the directory paths that you want to use and need to be enclosed in quotes if you have a space in a directory name. The /e switch copies all subdirectories and not just non-empty ones. Then, the xf *.* portion excludes all files from the copying process. The remaining options are added to help with getting around access issues and to try to copy only those directories that do not exist in the destination location. The /ftt switch was added to address the latter by causing ROBOCOPY to assume FAT file times. To get around the folder permission delays, the /r:0 switch was added to stop any operation being retried, with /w:0 setting wait times to 0 seconds. All this was enough to achieve what I wanted, and I am keeping it on file for my future reference, as well as sharing it with you.
Creating soft and hard symbolic links using the Windows command line
19th August 2015
In the world of UNIX and Linux, symbolic links are shortcuts, but they do not work like normal Windows shortcuts because you do not jump from one location to another with the file manager's address bar changing what it shows. Instead, it is as if you see the contents of the directory at another quicker to access location in the file system, and the same sort of thinking applies to files too. In some ways, it is like giving files and directories alternative aliases. There are soft links that point to the name of a given directory or file, and hard links that point to actual files or directories.
For a long time, I was under the mistaken impression that such things did not exist on Windows until I came across the mklink command, which came with the launch of Windows Vista at the start of 2007. While this feature might not be widely known, it demonstrates that Windows did adopt some UNIX and Linux capability long before other UNIX-like features, such as virtual desktops, were introduced in Windows 10.
By default, the aforementioned command sets up symbolic links to files and the /D switch allows the same to be done for directories too. The /H switch makes a hard link instead of a soft link, so we get much of the functionality of the ln command in UNIX and Linux. Here is an example that creates a soft symbolic link for a directory:
mklink /D shortcut target_directory
Above, shortcut is the name of the symbolic link file and target_directory is the destination to which it links. In my experience, it works best for destinations beyond your home folder and, from what I have read, hard links may not be possible across different disks either.
Setting up a WD My Book Live NAS on Ubuntu GNOME 13.10
1st December 2013
The official line from Western Digital is this: they do not support the use of their My Book Live NAS drives with Linux or UNIX. However, what that means is that they only develop tools for accessing their products for Windows and maybe OS X. It still doesn't mean that you cannot access the drive's configuration settings by pointing your web browser at http://mybooklive.local/. In fact, not having those extra tools is no drawback at all since the drive can be accessed through your file manager of choice under the Network section and the default name is MyBookLive too, so you easily can find the thing once it is connected to a router, or switch anyway.
Once you are in the server's web configuration area, you can do things like changing its name, updating its firmware, finding out what network has been assigned to it, creating and deleting file shares, password protecting file shares and other things. These are the kinds of things that come in handy if you are going to have a more permanent connection to the NAS from a PC that runs Linux. The steps that I describe have worked on Ubuntu 12.04 and 13.10 with the GNOME desktop environment.
What I was surprised to discover that you cannot just set up a symbolic link that points to a file share. Instead, it needs to be mounted and this can be done from the command line using mount or at start-up with /etc/fstab. For this to happen, you need the Common Internet File System utilities and these are added as follows if you need them (check in the Software Centre or in Synaptic):
sudo apt-get install cifs-utils
Once these are added, you can add a line like the following to /etc/fstab:
//[NAS IP address]/[file share name] /[file system mount point] cifs
credentials=[full file location]/.creds,
iocharset=utf8,
sec=ntlm,
gid=1000,
uid=1000,
file_mode=0775,
dir_mode=0775
0 0
Though I have broken it over several lines above, this is one unwrapped line in /etc/fstab with all the fields in square brackets populated for your system and with no brackets around these. Though there are other ways to specify the server, using its IP address is what has given me the most success; this is found under Settings > Network on the web console. Next up is the actual file share name on the NAS; I have used a custom term instead of the default of Public. The NAS file share needs to be mounted to an actual directory in your file system like /media/nas or whatever you like; however, you will need to create this beforehand. After that, you have to specify the file system, and it is cifs instead of more conventional alternatives like ext4 or swap. After this and before the final two space delimited zeroes in the line comes the chunk that deals with the security of the mount point.
What I have done in my case is to have a password-protected file share and the user ID and password have been placed in a file in my home area with only the owner having read and write permissions for it (600 in chmod-speak). Preceding the filename with a "." also affords extra invisibility. That file then is populated with the user ID and password like the following. Of course, the bracketed values have to be replaced with what you have in your case.
username=[NAS file share user ID]
password=[NAS file share password]
With the credentials file created, its options have to be set. First, there is the character set of the file (usually UTF-8 and I got error code 79 when I mistyped this) and the security that is to be applied to the credentials (ntlm in this case). To save having no write access to the mounted file share, the uid and gid for your user needs specification, with 1000 being the values for the first non-root user created on a Linux system. After that, it does no harm to set the file and directory permissions because they only can be set at mount time; using chmod, chown and chgrp afterwards, has no effect whatsoever. Here, I have set permissions to read, write and execute for the owner and the user group while only allowing read and execute access for everyone else (that's 775 in the world of chmod).
All of what I have described here worked for me and had to be gleaned from disparate sources like Mount Windows Shares Permanently from the Ubuntu Wiki, another blog entry regarding the permissions settings for a CIFS mount point and an Ubuntu forum posting on mounting CIFS with UTF-8 support. Because of the scattering of information, I just felt that it needed to all together in one place for others to use, and I hope that fulfils someone else's needs similarly to mine.
Relocating the Apache web server document root directory in Fedora 12
9th April 2010
So as not to deface anything that is available online on the web, I have a tendency to set up an offline Apache server on a home PC to do any tinkering away from the eyes of the unsuspecting public. Though Ubuntu is my mainstay for home computing, I do have a PC with Fedora installed, and I have been trying to get an Apache instance to start automatically on there unsuccessfully for a few months. While I can start it by running the following command as root, I'd rather not have more manual steps than is necessary.
httpd -k start
The command used by the system when it starts is different and, even when manually run as root, it failed with messages saying that it couldn't find the directory while the web server files are stored. Here it is:
service httpd start
The default document root location on any Linux distribution that I have seen is /var/www and all is very well with this, but it isn't a safe place to leave things if ever a re-installation is needed. Having needed to wipe /var after having it on a separate disk or partition for the sake of one installation, it doesn't look so persistent to me. In contrast, you can safeguard /home by having it on another disk or in a dedicated partition, which means that it can be retained even when you change the distro that you're using. Thus, I have got into the habit of having the root of the web server document root folder in my home area, and that is where I have been seeing the problem.
Because of the access message, I tried using chmod and chgrp, but to no avail. The remedy has to do with reassigning the security contexts used by SELinux. In Fedora, Apache will not work with the context user_home_t that is usually associated with home directories, but needs httpd_sys_content_t instead. To find out what contexts are associated with particular folders, issue the following command:
ls -Z
The final solution was to create a user account whose home directory hosts the root of the web server file system, called www in my case. Then, I executed the following command as root to get things going:
chcon -R -h -t httpd_sys_content_t /home/www
It appears that even the root of the home directory has to have an appropriate security context (/home has home_root_t so that might do the needful too). Without that, nothing will work, even if all is well at the next level down. The switches for chcon command translate as follows:
-R : recursive; applies changes to all files and folders within a directory.
-h : changes apply only to symbolic links and not to where they refer in the file system.
-t : alters context type.
It took a while for all of this stuff about SELinux security contexts to percolate through to the point where I was able to solve the problem. A spot of further inspiration was needed too and even guided my search for the information that I needed. It's well worth trying Linux Home Networking if you need further details. Though there are references to an earlier release of Fedora, the content still applies to later versions of Fedora to the current release, if my experience is typical.
Watch where you store your virtual machines when using VMware on Linux
12th July 2008
My experience is with Ubuntu on this one, but I have found that you need to be careful as regards the file system used by the drive where you keep your virtual machines. If it is NTFS, VMware can fail to start a VM because it cannot create a virtual memory file while it presents as physical memory to a guest operating system. Use ext2 or ext3 and there should be no problem, even if that means formatting a drive to fulfil the need. That's what I did and all was well thereafter.
The irritation of a 4 GB file size limitation
20th November 2007
Recently, I got myself a 500GB Western Digital My Book, an external hard drive in other words. Bizarrely, the thing is formatted using the FAT32 file system. While I appreciate that backward compatibility for Windows 9x might seem desirable, using NTFS would be more understandable, particularly given that the last of the 9x line, Windows ME, is now eight years old (there cannot be anybody who still uses that, can there?). The result is that I got core dump messages from cp commands issued from the terminal on my Ubuntu system to copy files of size exceeding 4GB last night. It surprised me at first, but it now seems to be a FAT32 limitation. The idea of formatting the drive as NTFS did occur to me, only for GParted not to do that, at least not with my current configuration. While the ext3 file system is an option, I have a spare PC with Windows 2000 so that will be a step too far for now, unless I take the plunge and bring that into the Linux universe too.
Other than the 4GB irritation, the new drive works well and was picked up and supported by Ubuntu without any hassle beyond getting it out of the box, finding a place for it on my desk and plugging in a few cables. While needing judiciousness about file sizes, it played an important role while I converted a 320 GB internal WD drive from NTFS to ext3 and may yet be vital if my Windows 2000 box gets a migration to Linux. In the interim, 500 GB is a lot of space, and having an external drive that size is a bonus these days. That is especially the case when you consider that the 1 terabyte threshold is on the verge of getting crossed. It certainly makes DVD's, flash drives and other multi-gigabyte media less impressive than they otherwise might appear.