Tuesday, March 31, 2015

cfdisk extra partition info

I have merged a new cfdisk(8) improvement. It allows to display/hide additional information about the current (selected) partition:
  • filesystem type, LABEL, UUID

    The important detail is that libblkid gathers the info by seeking on whole-disk device according to partition offsets from partition table -- so /dev/sda[n] devices do not have to exist or you can use cfdisk for disk images (e.g. "cfdisk file.img").
  • partition NAME, TYPE (hex/uuid and human readable name)
  • mountpoint -- for mounted filesystem as well as for not mounted (then from /etc/fstab)

All you need is press 'x'.  

The change is going to be available in util-linux v2.27 (May/Jun 2015). Thanks to Ondrej Oprala who has worked on this with me.

Friday, November 14, 2014

(s)fdisk scripts

Yesterday I merged support for sfdisk scripts to fdisk and cfdisk. Now it's possible to save your partitioning layout to text files and (re)use it in all fdisks.

It means that you don't have to start your partitioning from scratch in programs like cfdisk or fdisk, but you can reuse and finalize partitioning scenario already defined by sfdisk scripts. It may be attractive for DIY system installers, admins, etc.

All is based on libfdisk, so the same functionality may be very easily implemented in another tools too.

It's Friday ...sooo I tried to record video with some trivial example, all is from util-linux git tree (not yet release v2.26).


Monday, October 13, 2014

new sfdisk

The last partitioning tool from util-linux package without support for GPT (BSD, SGI, ...) and 4K disks was sfdisk. The situation was exactly the same like with cfdisk, it was impossible to incrementally improve the code, so the new version is written from scratch and based on libfdisk.

The most visible change is that the new sfdisk is all about sectors, it does not support obsolete Cylinder-Head-Sector addressing at all. This is no problem for users who use "--unit S", but if you still rely on old default cylinders than be careful with update. Frankly, LBA addressing is mandatory since ATA-3 (1997) and supported by Linux since beginning.

The new sfdisk also does not support some obscure or rarely used options like
--DOS, --IBM, --DOS-extended, --unhide, --show-extended, --cylinders, --heads, --sectors, --inside-outer, --not-inside-outer.

The last incompatibility is in backup mode. The old implementation uses sfdisk specific backup files. The new implementation uses the same concept like "wipefs --backup". The data are stored to ~/sfdisk-dev-offset.bak by default and it's possible to use dd(1) to restore your partition table or so. The backup files contains only data from the device, nothing else.  For example:
# sfdisk --backup /dev/sdb
...
Backup files:
        PMBR (offset     0, size   512): /root/sfdisk-sdb-0x00000000.bak
  GPT Header (offset   512, size   512): /root/sfdisk-sdb-0x00000200.bak
 GPT Entries (offset  1024, size 16384): /root/sfdisk-sdb-0x00000400.bak
...
and to restore:
 
 # dd if=~/sfdisk-sda-0x00000200.bak of=/dev/sdb \
      seek=$((0x00000200.bak)) bs=1 conv=notrunc 

All is described in the sfdisk man page. The another change is possibility to specify partition sizes in human readable notation {K,M,G,T...}, for example

# sfdisk /dev/sdb <<EOF
label: gpt
, 10G
, 10G
EOF

creates two 10GiB partitions. Note that default is to align all partitions to I/O limits (e.g. physical sector size). The first partition offset is by default 1MiB (e.g. 2048 512-byte-sectors). The partitions are by default aligned to megabytes. The same concept we use for fdisk and cfdisk (and parted probably too).

The default is DOS (MBR) disk label. If you want to use GPT then just add "--label gpt" to the command line or "label: gpt" to the script. The partition type shortcuts like 'L' (for Linux) or 'S' (for swap area) work for MBR as well as for GPT. If you want something else then you can use GUID for GPT or hex codes for MBR.

The new sfdisk supports nested disk labels. This is important for people who use BSD disk labels or hybrid GPT. The new command line option "--label-nested dos" forces sfdisk to modify protective MBR rather than the default GPT disk label. It means that you can manually create hybrid GPT. (No, we don't plan to add any "translate GPT to MBR" high-level feature for hybrid disks, hybrid GPT sucks.)

The nice new feature is that sfdisk allows to add new partitions to your partition table rather than always create whole partition table from scratch, all you need is the new --append command line option.

The important feature is that you can define your own output format for --list by new command line option "--output columns". sfdisk shares this new feature with fdisk where -o modifies 'p'rint output, for example:

 
# sfdisk --quiet --list -o DEVICE,SIZE,TYPE /dev/sda
Device      Size Type
/dev/sda1  1000M EFI System
/dev/sda2     2G Microsoft basic data
/dev/sda3   9.7G Linux swap
/dev/sda4  34.2G Microsoft basic data
/dev/sda5  63.2G Microsoft basic data
/dev/sda6  39.1G Microsoft basic data

You probably already know this concept from lsblk or findmnt. It's also supported to extend the default output by "-o+" notation, for example "fdisk --list -o+UUID /dev/sda" to see UUIDs for GPT partitions. 

Another features:
  • --part-uuid print or change GPT partition UUID
  • --part-type (or original --id) print or change partition type
  • --part-label print or changes GPT partition label (name)
  • --part-attrs print or change GPT partition attribute bites

The script parsing and --dump functionality is within libfdisk. The goal is to support partitioning dumps in fdisk and cfdisk too. It is going to be possible to "sfdisk --dump /dev/sda > foo" and then read the "foo" file to cfdisk or fdisk. And vice-versa, you can compose all your partition table by user-friendly cfdisk, save to the script file (rather than to device) and later use the file by sfdisk, etc.

Wednesday, August 6, 2014

zramctl

I merged zramctl tool a few days ago. It's based on original code from Timofey Titovets and the idea is the same as for losetup(8). zRam was merged to Linux kernel 3.14; the zram devices use RAM to create compressed block devices. The zramctl provides user friendly command line interface to create, reset and list the devices.

It's pretty simple and easy to use from userspace. See example below (kernel 3.15.7-200.fc20)
 
# modprobe zram num_devices=4
  
# zramctl --find --size 10M
/dev/zram0
 
# mkfs.ext2 -q /dev/zram0
# mount /dev/zram0 /mnt/test
  
./zramctl --find --size 10M --streams 2
/dev/zram1
 
# mkswap /dev/zram1
Setting up swapspace version 1, size = 10236 KiB
no label, UUID=776a95b7-5876-4be4-a66b-9b869cf35bd1
# swapon UUID=776a95b7-5876-4be4-a66b-9b869cf35bd1
  
# zramctl
NAME       ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT
/dev/zram0 lzo            10M  40K  797B   40K       1 /mnt/test
/dev/zram1 lzo            10M   4K   78B    4K       2 [SWAP]

Note that kernel 3.14 does not support more compression streams and algorithms selection.

The next step will be probably to support zram initialization in swapon(8) to
make it easy for users to define swap on zram in /etc/fstab.


Friday, June 20, 2014

new cfdisk (util-linux v2.25)

cfdisk is a popular ncurses partitioning tool. Unfortunately, it has been ignored by developers for many many years. The original version does not a have clue
about 4K disks, modern disk I/O limits (alignment offset, optimal I/O sizes, etc),
and it was all about MBR (DOS) only.

It was impossible to improve the old code by refactoring, so the new version is written from scratch. The new cfdisk is based on on the same code like fdisk, so it shares all the necessary features required for new disks and it supports MBR, GPT, SGI and SUN disk labels. Some features have been removed:
  • it does not have a clue about CHS addressing any more
  • it's impossible to play any games with disk geometry (use fdisk if you believe that CHS setting makes any sense)
  • 'm' command (maximize disk usage of the current partition) is not implemented
  • 'p' command and --print command line option are not implemented (use partx or lsblk)
  •  'u' (units) command is not implemented, all is based on sectors or real sizes
The idea is to keep cfdisk pretty simple and easy to use for end users. Advanced users or users who want to do some unusual things have to use fdisk or parted.

New features:
  • output formatting based on libsmartcols
  • tree-like output for MBR extended and logical partitions
  • show free space on place where the gap is really located
  • colors
  • new 's'ort command to reorder partition according to start sectors
  • partitions aligned to I/O limits, 1MiB start offset, etc.
  • it's still possible to recompile with slang library (although I personallyprefer ncursesw)

For full size screenshots see g+

What next? sfdisk and stable public API fro libfdisk... let's wait for v2.26 :-)




Friday, May 30, 2014

libsmartcols - pretty output for everyone!

util-linux 2.25 is going to contain libsmartcols. The library code is based on code originally developed for lsblk(8), findmnt(8), lslocks(8) etc.  The goal is to share formatting code to print pretty tables and trees.

Features:
  • tree-like output (see lsblk(8) or findmnt(8))
  • table-like output (see lslocks(8))
  • formatting sensitive to terminal width
  • fully supports UTF8 (correctly truncate data in cells, tree lines, ...)
  • dynamic or fixed columns width
  • truncate data in cell on demand
  • raw (no formatting) output mode
  • NAME=value output mode
  • custom cells and lines delimiters (for example for CSV output)
  • built-in ASCII, UTF8 or custom symbols to draw trees
  • per column, line or cell colors
  • colors specified by words (e.g. "red") or ESC sequences
  • sort lines
  • enable/disable heading
  • output to FILE stream (default stdout), or to string
  • all columns, lines and cells accessible by iterators (no callbacks)
  • output data specified by strings (no crazy unions or to-string conversion functions in the library)
  • reference counting
  • integrated debug output (sensitive to LIBSMARTCOLS_DEBUG env)
  • usable to keep parent<->child relationship
  • library symbols versioning (no soname changes)

See bellow a trivial (so no errors handling, etc.) example.

int main(void)
{
        struct libscols_table *tb;
        struct libscols_line *ln, *dad, *gdad;
        enum { COL_NAME, COL_AGE };

        setlocale(LC_ALL, "");

        tb = scols_new_table();
        scols_table_new_column(tb, "NAME", 0.1, SCOLS_FL_TREE);
        scols_table_new_column(tb, "AGE",     2, SCOLS_FL_RIGHT);

        ln = gdad = scols_table_new_line(tb, NULL);
        scols_line_set_data(ln, COL_NAME, "Grandfather Bob");
        scols_line_set_data(ln, COL_AGE, "61");

        ln = dad = scols_table_new_line(tb, ln);
        scols_line_set_data(ln, COL_NAME, "Father Adam");
        scols_line_set_data(ln, COL_AGE, "38");

        ln = scols_table_new_line(tb, dad);
        scols_line_set_data(ln, COL_NAME, "Baby Val");
        scols_line_set_data(ln, COL_AGE, "9");

        ln = scols_table_new_line(tb, dad);
        scols_line_set_data(ln, COL_NAME, "Baby Dilbert");
        scols_line_set_data(ln, COL_AGE, "5");

        ln = scols_table_new_line(tb, gdad);
        scols_line_set_data(ln, COL_NAME, "Aunt Gaga");
        scols_line_set_data(ln, COL_AGE, "35");

        scols_print_table(tb);
        scols_unref_table(tb);
        return 0;
}

... and output:

NAME             AGE
Grandfather Bob   61
├─Father Adam     38
│ ├─Baby Val       9
│ └─Baby Dilbert   5
└─Aunt Gaga       35 

Tuesday, April 1, 2014

terminal-colors.d

I have already talked about it at g+. For util-linux we don't want to follow the current strange behavior when command-line utils have disabled colors by default, but distributions use shell aliases in profile files to revert the default.

It does not mean that we want ignore color blind people, obscure terminals or people who just don't like colors. The solution is to provide simple, elegant and package independent way how to control (disable) colorized output. And yes, aliases are not elegant.

The next util-linux release is going to introduce /etc/terminal-colors.d directory
to control colors for terminal utils. It's pretty simple:

Synopsis:
/etc/terminal-colors.d/[name.]disable
/etc/terminal-colors.d/name.enable
Examples:
  •  disable colors for all utils:
    # touch /etc/terminal-colors.d/disable 
    
  • disable colors for dmesg(1):
    # touch /etc/terminal-colors.d/dmesg.disable
  • disable colors for all utils except dmesg(1):
    # touch /etc/terminal-colors.d/disable
    # touch /etc/terminal-colors.d/dmesg.enable
For utils from util-linux the command line option --color[={auto,never,always}] overrides the setting from terminal-colors.d (so if you for some reason love shell aliases then it's still possible...).

The terminal-colors.d concept is completely open, it would be nice to see it supported in another projects (hint: gcc, grep, coreutils:-) too. It's so trivial that all you need is a few access(F_OK) calls. The thing we maintain in util-linux is terminal-colors.d.5 man page only.

Maybe later for util-linux we will also use the directory (or/and copy in $HOME) to store color schemes.

Keep your Bike-sheds colorized! :-)

UPDATE: since v2.25:
  • $XDG_CONFIG_HOME/terminal-colors.d  or  $HOME/.config/terminal-colors.d overrides the global setting
  • terminal-colors.d is possible to use for color schemes
        echo 'alert 37;41' >> /etc/terminal-colors.d/dmesg.scheme
    changes color used for kernel alerts in dmesg output
  • synopsis is /etc/terminal-colors.d/[[name][@term].][type], it means that for example /etc/terminal-colors.d/@vt100.disable disables colors for all vt100 terminals
  • we have terminal-colors.d(5) man page with all details